1 <!doctype linuxdoc system>
4 <title>ca65 Users Guide
5 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
6 <date>2000-07-19, 2000-11-29, 2001-10-02, 2005-09-08
9 ca65 is a powerful macro assembler for the 6502, 65C02 and 65816 CPUs. It is
10 used as a companion assembler for the cc65 crosscompiler, but it may also be
11 used as a standalone product.
14 <!-- Table of contents -->
17 <!-- Begin the document -->
21 ca65 is a replacement for the ra65 assembler that was part of the cc65 C
22 compiler, originally developed by John R. Dunning. I had some problems with
23 ra65 and the copyright does not permit some things which I wanted to be
24 possible, so I decided to write a completely new assembler/linker/archiver
25 suite for the cc65 compiler. ca65 is part of this suite.
27 Some parts of the assembler (code generation and some routines for symbol
28 table handling) are taken from an older crossassembler named a816 written
29 by me a long time ago.
32 <sect1>Design criteria<p>
34 Here's a list of the design criteria, that I considered important for the
39 <item> The assembler must support macros. Macros are not essential, but they
40 make some things easier, especially when you use the assembler in the
41 backend of a compiler.
42 <item> The assembler must support the newer 65C02 and 65816 CPUs. I have been
43 thinking about a 65816 backend for the C compiler, and even my old
44 a816 assembler had support for these CPUs, so this wasn't really a
46 <item> The assembler must produce relocatable code. This is necessary for the
47 compiler support, and it is more convenient.
48 <item> Conditional assembly must be supported. This is a must for bigger
49 projects written in assembler (like Elite128).
50 <item> The assembler must support segments, and it must support more than
51 three segments (this is the count, most other assemblers support).
52 Having more than one code segments helps developing code for systems
53 with a divided ROM area (like the C64).
54 <item> The linker must be able to resolve arbitrary expressions. It should
55 be able to get things like
62 <item> True lexical nesting for symbols. This is very convenient for larger
64 <item> "Cheap" local symbols without lexical nesting for those quick, late
66 <item> I liked the idea of "options" as Anre Fachats .o65 format has it, so I
67 introduced the concept into the object file format use by the new cc65
69 <item> The assembler will be a one pass assembler. There was no real need for
70 this decision, but I've written several multipass assemblers, and it
71 started to get boring. A one pass assembler needs much more elaborated
72 data structures, and because of that it's much more fun:-)
73 <item> Non-GPLed code that may be used in any project without restrictions or
74 fear of "GPL infecting" other code.
82 <sect1>Command line option overview<p>
84 The assembler accepts the following options:
87 ---------------------------------------------------------------------------
88 Usage: ca65 [options] file
90 -D name[=value] Define a symbol
91 -I dir Set an include directory search path
92 -U Mark unresolved symbols as import
93 -V Print the assembler version
94 -W n Set warning level n
95 -g Add debug info to object file
97 -i Ignore case of symbols
98 -l Create a listing if assembly was ok
99 -mm model Set the memory model
100 -o name Name the output file
102 -t sys Set the target system
103 -v Increase verbosity
106 --auto-import Mark unresolved symbols as import
107 --bin-include-dir dir Set a search path for binary includes
108 --cpu type Set cpu type
109 --create-dep name Create a make dependency file
110 --create-full-dep name Create a full make dependency file
111 --debug-info Add debug info to object file
112 --feature name Set an emulation feature
113 --forget-inc-paths Forget include search paths
114 --help Help (this text)
115 --ignore-case Ignore case of symbols
116 --include-dir dir Set an include directory search path
117 --listing Create a listing if assembly was ok
118 --list-bytes n Maximum number of bytes per listing line
119 --macpack-dir dir Set a macro package directory
120 --memory-model model Set the memory model
121 --pagelength n Set the page length for the listing
122 --smart Enable smart mode
123 --target sys Set the target system
124 --verbose Increase verbosity
125 --version Print the assembler version
126 ---------------------------------------------------------------------------
130 <sect1>Command line options in detail<p>
132 Here is a description of all the command line options:
136 <label id="option--bin-include-dir">
137 <tag><tt>--bin-include-dir dir</tt></tag>
139 Name a directory which is searched for binary include files. The option
140 may be used more than once to specify more than one directory to search. The
141 current directory is always searched first before considering any
142 additional directories. See also the section about <ref id="search-paths"
143 name="search paths">.
146 <label id="option--cpu">
147 <tag><tt>--cpu type</tt></tag>
149 Set the default for the CPU type. The option takes a parameter, which
152 6502, 65SC02, 65C02, 65816, sunplus, sweet16, HuC6280
154 The sunplus cpu is not available in the freeware version, because the
155 instruction set is "proprietary and confidential".
158 <label id="option-create-dep">
159 <tag><tt>--create-dep name</tt></tag>
161 Tells the assembler to generate a file containing the dependency list for
162 the assembled module in makefile syntax. The output is written to a file
163 with the given name. The output does not include files passed via debug
164 information to the assembler.
167 <label id="option-create-full-dep">
168 <tag><tt>--create-full-dep name</tt></tag>
170 Tells the assembler to generate a file containing the dependency list for
171 the assembled module in makefile syntax. The output is written to a file
172 with the given name. The output does include files passed via debug
173 information to the assembler.
176 <label id="option--feature">
177 <tag><tt>--feature name</tt></tag>
179 Enable an emulation feature. This is identical as using <tt/.FEATURE/
180 in the source with two exceptions: Feature names must be lower case, and
181 each feature must be specified by using an extra <tt/--feature/ option,
182 comma separated lists are not allowed.
184 See the discussion of the <tt><ref id=".FEATURE" name=".FEATURE"></tt>
185 command for a list of emulation features.
188 <label id="option--forget-inc-paths">
189 <tag><tt>--forget-inc-paths</tt></tag>
191 Forget the builtin include paths. This is most useful when building
192 customized assembler modules, in which case the standard header files should
196 <label id="option-g">
197 <tag><tt>-g, --debug-info</tt></tag>
199 When this option (or the equivalent control command <tt/.DEBUGINFO/) is
200 used, the assembler will add a section to the object file that contains
201 all symbols (including local ones) together with the symbol values and
202 source file positions. The linker will put these additional symbols into
203 the VICE label file, so even local symbols can be seen in the VICE
207 <label id="option-h">
208 <tag><tt>-h, --help</tt></tag>
210 Print the short option summary shown above.
213 <label id="option-i">
214 <tag><tt>-i, --ignore-case</tt></tag>
216 This option makes the assembler case insensitive on identifiers and labels.
217 This option will override the default, but may itself be overridden by the
218 <tt><ref id=".CASE" name=".CASE"></tt> control command.
221 <label id="option-l">
222 <tag><tt>-l, --listing</tt></tag>
224 Generate an assembler listing. The listing file will always have the
225 name of the main input file with the extension replaced by ".lst". This
226 may change in future versions.
229 <label id="option--list-bytes">
230 <tag><tt>--list-bytes n</tt></tag>
232 Set the maximum number of bytes printed in the listing for one line of
233 input. See the <tt><ref id=".LISTBYTES" name=".LISTBYTES"></tt> directive
234 for more information. The value zero can be used to encode an unlimited
235 number of printed bytes.
238 <label id="option--macpack-dir">
239 <tag><tt>--macpack-dir dir</tt></tag>
241 This options allows to specify a directory containing macro files that are
242 used instead of the builtin images when a <tt><ref id=".MACPACK"
243 name=".MACPACK"></tt> directive is encountered. If <tt>--macpack-dir</tt>
244 was specified, a <tt>.mac</tt> extension is added to the package name and
245 the resulting file is loaded from the given directory. This is most useful
246 when debugging the builtin macro packages.
249 <label id="option-mm">
250 <tag><tt>-mm model, --memory-model model</tt></tag>
252 Define the default memory model. Possible model specifiers are near, far and
256 <label id="option-o">
257 <tag><tt>-o name</tt></tag>
259 The default output name is the name of the input file with the extension
260 replaced by ".o". If you don't like that, you may give another name with
261 the -o option. The output file will be placed in the same directory as
262 the source file, or, if -o is given, the full path in this name is used.
265 <label id="option--pagelength">
266 <tag><tt>--pagelength n</tt></tag>
268 sets the length of a listing page in lines. See the <tt><ref
269 id=".PAGELENGTH" name=".PAGELENGTH"></tt> directive for more information.
272 <label id="option-s">
273 <tag><tt>-s, --smart-mode</tt></tag>
275 In smart mode (enabled by -s or the <tt><ref id=".SMART" name=".SMART"></tt>
276 pseudo instruction) the assembler will track usage of the <tt/REP/ and
277 <tt/SEP/ instructions in 65816 mode and update the operand sizes
278 accordingly. If the operand of such an instruction cannot be evaluated by
279 the assembler (for example, because the operand is an imported symbol), a
282 Beware: Since the assembler cannot trace the execution flow this may
283 lead to false results in some cases. If in doubt, use the .ixx and .axx
284 instructions to tell the assembler about the current settings. Smart
285 mode is off by default.
288 <label id="option-t">
289 <tag><tt>-t sys, --target sys</tt></tag>
291 Set the target system. This will enable translation of character strings
292 and character constants into the character set of the target platform.
293 The default for the target system is "none", which means that no translation
294 will take place. The assembler supports the same target systems as the
295 compiler, see there for a list.
298 <label id="option-v">
299 <tag><tt>-v, --verbose</tt></tag>
301 Increase the assembler verbosity. Usually only needed for debugging
302 purposes. You may use this option more than one time for even more
306 <label id="option-D">
307 <tag><tt>-D</tt></tag>
309 This option allows you to define symbols on the command line. Without a
310 value, the symbol is defined with the value zero. When giving a value,
311 you may use the '$' prefix for hexadecimal symbols. Please note
312 that for some operating systems, '$' has a special meaning, so
313 you may have to quote the expression.
316 <label id="option-I">
317 <tag><tt>-I dir, --include-dir dir</tt></tag>
319 Name a directory which is searched for include files. The option may be
320 used more than once to specify more than one directory to search. The
321 current directory is always searched first before considering any
322 additional directories. See also the section about <ref id="search-paths"
323 name="search paths">.
326 <label id="option-U">
327 <tag><tt>-U, --auto-import</tt></tag>
329 Mark symbols that are not defined in the sources as imported symbols. This
330 should be used with care since it delays error messages about typos and such
331 until the linker is run. The compiler uses the equivalent of this switch
332 (<tt><ref id=".AUTOIMPORT" name=".AUTOIMPORT"></tt>) to enable auto imported
333 symbols for the runtime library. However, the compiler is supposed to
334 generate code that runs through the assembler without problems, something
335 which is not always true for assembler programmers.
338 <label id="option-V">
339 <tag><tt>-V, --version</tt></tag>
341 Print the version number of the assembler. If you send any suggestions
342 or bugfixes, please include the version number.
345 <label id="option-W">
346 <tag><tt>-Wn</tt></tag>
348 Set the warning level for the assembler. Using -W2 the assembler will
349 even warn about such things like unused imported symbols. The default
350 warning level is 1, and it would probably be silly to set it to
358 <sect>Search paths<label id="search-paths"><p>
360 Normal include files are searched in the following places:
363 <item>The current directory.
364 <item>A compiled-in directory, which is often <tt>/usr/lib/cc65/asminc</tt>
366 <item>The value of the environment variable <tt/CA65_INC/ if it is defined.
367 <item>A subdirectory named <tt/asminc/ of the directory defined in the
368 environment variable <tt/CC65_HOME/, if it is defined.
369 <item>Any directory added with the <tt/<ref id="option-I" name="-I">/ option
373 Binary include files are searched in the following places:
376 <item>The current directory.
377 <item>Any directory added with the <tt/<ref id="option--bin-include-dir"
378 name="--bin-include-dir">/ option on the command line.
383 <sect>Input format<p>
385 <sect1>Assembler syntax<p>
387 The assembler accepts the standard 6502/65816 assembler syntax. One line may
388 contain a label (which is identified by a colon), and, in addition to the
389 label, an assembler mnemonic, a macro, or a control command (see section <ref
390 id="control-commands" name="Control Commands"> for supported control
391 commands). Alternatively, the line may contain a symbol definition using
392 the '=' token. Everything after a semicolon is handled as a comment (that is,
395 Here are some examples for valid input lines:
398 Label: ; A label and a comment
399 lda #$20 ; A 6502 instruction plus comment
400 L1: ldx #$20 ; Same with label
401 L2: .byte "Hello world" ; Label plus control command
402 mymac $20 ; Macro expansion
403 MySym = 3*L1 ; Symbol definition
404 MaSym = Label ; Another symbol
407 The assembler accepts
410 <item>all valid 6502 mnemonics when in 6502 mode (the default or after the
411 <tt><ref id=".P02" name=".P02"></tt> command was given).
412 <item>all valid 6502 mnemonics plus a set of illegal instructions when in
413 <ref id="6502X-mode" name="6502X mode">.
414 <item>all valid 65SC02 mnemonics when in 65SC02 mode (after the
415 <tt><ref id=".PSC02" name=".PSC02"></tt> command was given).
416 <item>all valid 65C02 mnemonics when in 65C02 mode (after the
417 <tt><ref id=".PC02" name=".PC02"></tt> command was given).
418 <item>all valid 65618 mnemonics when in 65816 mode (after the
419 <tt><ref id=".P816" name=".P816"></tt> command was given).
420 <item>all valid SunPlus mnemonics when in SunPlus mode (after the
421 <tt><ref id=".SUNPLUS" name=".SUNPLUS"></tt> command was given).
427 In 65816 mode several aliases are accepted in addition to the official
431 BGE is an alias for BCS
432 BLT is an alias for BCC
433 CPA is an alias for CMP
434 DEA is an alias for DEC A
435 INA is an alias for INC A
436 SWA is an alias for XBA
437 TAD is an alias for TCD
438 TAS is an alias for TCS
439 TDA is an alias for TDC
440 TSA is an alias for TSC
445 <sect1>6502X mode<label id="6502X-mode"><p>
447 6502X mode is an extension to the normal 6502 mode. In this mode, several
448 mnemonics for illegal instructions of the NMOS 6502 CPUs are accepted. Since
449 these instructions are illegal, there are no official mnemonics for them. The
450 unofficial ones are taken from <htmlurl
451 url="http://oxyron.net/graham/opcodes02.html"
452 name="http://oxyron.net/graham/opcodes02.html">. Please note that only the
453 ones marked as "stable" are supported. The following table uses information
454 from the mentioned web page, for more information, see there.
457 <item><tt>ALR: A:=(A and #{imm})*2;</tt>
458 <item><tt>ANC: A:=A and #{imm};</tt> Generates opcode $0B.
459 <item><tt>ARR: A:=(A and #{imm})/2;</tt>
460 <item><tt>AXS: X:=A and X-#{imm};</tt>
461 <item><tt>DCP: {adr}:={adr}-1; A-{adr};</tt>
462 <item><tt>ISC: {adr}:={adr}+1; A:=A-{adr};</tt>
463 <item><tt>LAS: A,X,S:={adr} and S;</tt>
464 <item><tt>LAX: A,X:={adr};</tt>
465 <item><tt>RLA: {adr}:={adr}rol; A:=A and {adr};</tt>
466 <item><tt>RRA: {adr}:={adr}ror; A:=A adc {adr};</tt>
467 <item><tt>SAX: {adr}:=A and X;</tt>
468 <item><tt>SLO: {adr}:={adr}*2; A:=A or {adr};</tt>
469 <item><tt>SRE: {adr}:={adr}/2; A:=A xor {adr};</tt>
474 <sect1>sweet16 mode<label id="sweet16-mode"><p>
476 SWEET 16 is an interpreter for a pseudo 16 bit CPU written by Steve Wozniak
477 for the Apple ][ machines. It is available in the Apple ][ ROM. ca65 can
478 generate code for this pseudo CPU when switched into sweet16 mode. The
479 following is special in sweet16 mode:
483 <item>The '@' character denotes indirect addressing and is no longer available
484 for cheap local labels. If you need cheap local labels, you will have to
485 switch to another lead character using the <tt/<ref id=".LOCALCHAR"
486 name=".LOCALCHAR">/ command.
488 <item>Registers are specified using <tt/R0/ .. <tt/R15/. In sweet16 mode,
489 these identifiers are reserved words.
493 Please note that the assembler does neither supply the interpreter needed for
494 SWEET 16 code, nor the zero page locations needed for the SWEET 16 registers,
495 nor does it call the interpreter. All this must be done by your program. Apple
496 ][ programmers do probably know how to use sweet16 mode.
498 For more information about SWEET 16, see
499 <htmlurl url="http://www.6502.org/source/interpreters/sweet16.htm"
500 name="http://www.6502.org/source/interpreters/sweet16.htm">.
503 <sect1>Number format<p>
505 For literal values, the assembler accepts the widely used number formats: A
506 preceding '$' or a trailing 'h' denotes a hex value, a preceding '%'
507 denotes a binary value, and a bare number is interpreted as a decimal. There
508 are currently no octal values and no floats.
511 <sect1>Conditional assembly<p>
513 Please note that when using the conditional directives (<tt/.IF/ and friends),
514 the input must consist of valid assembler tokens, even in <tt/.IF/ branches
515 that are not assembled. The reason for this behaviour is that the assembler
516 must still be able to detect the ending tokens (like <tt/.ENDIF/), so
517 conversion of the input stream into tokens still takes place. As a consequence
518 conditional assembly directives may <bf/not/ be used to prevent normal text
519 (used as a comment or similar) from being assembled. <p>
525 <sect1>Expression evaluation<p>
527 All expressions are evaluated with (at least) 32 bit precision. An
528 expression may contain constant values and any combination of internal and
529 external symbols. Expressions that cannot be evaluated at assembly time
530 are stored inside the object file for evaluation by the linker.
531 Expressions referencing imported symbols must always be evaluated by the
535 <sect1>Size of an expression result<p>
537 Sometimes, the assembler must know about the size of the value that is the
538 result of an expression. This is usually the case, if a decision has to be
539 made, to generate a zero page or an absolute memory references. In this
540 case, the assembler has to make some assumptions about the result of an
544 <item> If the result of an expression is constant, the actual value is
545 checked to see if it's a byte sized expression or not.
546 <item> If the expression is explicitly casted to a byte sized expression by
547 one of the '>', '<' or '^' operators, it is a byte expression.
548 <item> If this is not the case, and the expression contains a symbol,
549 explicitly declared as zero page symbol (by one of the .importzp or
550 .exportzp instructions), then the whole expression is assumed to be
552 <item> If the expression contains symbols that are not defined, and these
553 symbols are local symbols, the enclosing scopes are searched for a
554 symbol with the same name. If one exists and this symbol is defined,
555 it's attributes are used to determine the result size.
556 <item> In all other cases the expression is assumed to be word sized.
559 Note: If the assembler is not able to evaluate the expression at assembly
560 time, the linker will evaluate it and check for range errors as soon as
564 <sect1>Boolean expressions<p>
566 In the context of a boolean expression, any non zero value is evaluated as
567 true, any other value to false. The result of a boolean expression is 1 if
568 it's true, and zero if it's false. There are boolean operators with extreme
569 low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/
570 operators are shortcut operators. That is, if the result of the expression is
571 already known, after evaluating the left hand side, the right hand side is
575 <sect1>Constant expressions<p>
577 Sometimes an expression must evaluate to a constant without looking at any
578 further input. One such example is the <tt/<ref id=".IF" name=".IF">/ command
579 that decides if parts of the code are assembled or not. An expression used in
580 the <tt/.IF/ command cannot reference a symbol defined later, because the
581 decision about the <tt/.IF/ must be made at the point when it is read. If the
582 expression used in such a context contains only constant numerical values,
583 there is no problem. When unresolvable symbols are involved it may get harder
584 for the assembler to determine if the expression is actually constant, and it
585 is even possible to create expressions that aren't recognized as constant.
586 Simplifying the expressions will often help.
588 In cases where the result of the expression is not needed immediately, the
589 assembler will delay evaluation until all input is read, at which point all
590 symbols are known. So using arbitrary complex constant expressions is no
591 problem in most cases.
595 <sect1>Available operators<label id="operators"><p>
599 <bf/Operator/| <bf/Description/| <bf/Precedence/@<hline>
600 | Built-in string functions| 0@
602 | Built-in pseudo-variables| 1@
603 | Built-in pseudo-functions| 1@
604 +| Unary positive| 1@
605 -| Unary negative| 1@
607 .BITNOT| Unary bitwise not| 1@
609 .LOBYTE| Unary low-byte operator| 1@
611 .HIBYTE| Unary high-byte operator| 1@
613 .BANKBYTE| Unary bank-byte operator| 1@
615 *| Multiplication| 2@
617 .MOD| Modulo operator| 2@
619 .BITAND| Bitwise and| 2@
621 .BITXOR| Binary bitwise xor| 2@
623 .SHL| Shift-left operator| 2@
625 .SHR| Shift-right operator| 2@
627 +| Binary addition| 3@
628 -| Binary subtraction| 3@
630 .BITOR| Bitwise or| 3@
632 = | Compare operator (equal)| 4@
633 <>| Compare operator (not equal)| 4@
634 <| Compare operator (less)| 4@
635 >| Compare operator (greater)| 4@
636 <=| Compare operator (less or equal)| 4@
637 >=| Compare operator (greater or equal)| 4@
640 .AND| Boolean and| 5@
641 .XOR| Boolean xor| 5@
643 ||<newline>
647 .NOT| Boolean not| 7@<hline>
649 <caption>Available operators, sorted by precedence
652 To force a specific order of evaluation, parentheses may be used, as usual.
656 <sect>Symbols and labels<p>
658 A symbol or label is an identifier that starts with a letter and is followed
659 by letters and digits. Depending on some features enabled (see
660 <tt><ref id="at_in_identifiers" name="at_in_identifiers"></tt>,
661 <tt><ref id="dollar_in_identifiers" name="dollar_in_identifiers"></tt> and
662 <tt><ref id="leading_dot_in_identifiers" name="leading_dot_in_identifiers"></tt>)
663 other characters may be present. Use of identifiers consisting of a single
664 character will not work in all cases, because some of these identifiers are
665 reserved keywords (for example "A" is not a valid identifier for a label,
666 because it is the keyword for the accumulator).
668 The assembler allows you to use symbols instead of naked values to make
669 the source more readable. There are a lot of different ways to define and
670 use symbols and labels, giving a lot of flexibility.
672 <sect1>Numeric constants<p>
674 Numeric constants are defined using the equal sign or the label assignment
675 operator. After doing
681 may use the symbol "two" in every place where a number is expected, and it is
682 evaluated to the value 2 in this context. The label assignment operator causes
683 the same, but causes the symbol to be marked as a label, which may cause a
684 different handling in the debugger:
690 The right side can of course be an expression:
697 <sect1>Standard labels<p>
699 A label is defined by writing the name of the label at the start of the line
700 (before any instruction mnemonic, macro or pseudo directive), followed by a
701 colon. This will declare a symbol with the given name and the value of the
702 current program counter.
705 <sect1>Local labels and symbols<p>
707 Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to
708 create regions of code where the names of labels and symbols are local to this
709 region. They are not known outside of this region and cannot be accessed from
710 there. Such regions may be nested like PROCEDUREs in Pascal.
712 See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
713 directive for more information.
716 <sect1>Cheap local labels<p>
718 Cheap local labels are defined like standard labels, but the name of the
719 label must begin with a special symbol (usually '@', but this can be
720 changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt>
723 Cheap local labels are visible only between two non cheap labels. As soon as a
724 standard symbol is encountered (this may also be a local symbol if inside a
725 region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the
726 cheap local symbol goes out of scope.
728 You may use cheap local labels as an easy way to reuse common label
729 names like "Loop". Here is an example:
732 Clear: lda #$00 ; Global label
734 @Loop: sta Mem,y ; Local label
738 Sub: ... ; New global label
739 bne @Loop ; ERROR: Unknown identifier!
742 <sect1>Unnamed labels<p>
744 If you really want to write messy code, there are also unnamed labels. These
745 labels do not have a name (you guessed that already, didn't you?). A colon is
746 used to mark the absence of the name.
748 Unnamed labels may be accessed by using the colon plus several minus or plus
749 characters as a label designator. Using the '-' characters will create a back
750 reference (use the n'th label backwards), using '+' will create a forward
751 reference (use the n'th label in forward direction). An example will help to
774 As you can see from the example, unnamed labels will make even short
775 sections of code hard to understand, because you have to count labels
776 to find branch targets (this is the reason why I for my part do
777 prefer the "cheap" local labels). Nevertheless, unnamed labels are
778 convenient in some situations, so it's your decision.
781 <sect1>Using macros to define labels and constants<p>
783 While there are drawbacks with this approach, it may be handy in some
784 situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is
785 possible to define symbols or constants that may be used elsewhere. Since
786 the macro facility works on a very low level, there is no scoping. On the
787 other side, you may also define string constants this way (this is not
788 possible with the other symbol types).
794 .DEFINE version "SOS V2.3"
796 four = two * two ; Ok
799 .PROC ; Start local scope
800 two = 3 ; Will give "2 = 3" - invalid!
805 <sect1>Symbols and <tt>.DEBUGINFO</tt><p>
807 If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref
808 id="option-g" name="-g"> is given on the command line), global, local and
809 cheap local labels are written to the object file and will be available in the
810 symbol file via the linker. Unnamed labels are not written to the object file,
811 because they don't have a name which would allow to access them.
815 <sect>Scopes<label id="scopes"><p>
817 ca65 implements several sorts of scopes for symbols.
819 <sect1>Global scope<p>
821 All (non cheap local) symbols that are declared outside of any nested scopes
825 <sect1>Cheap locals<p>
827 A special scope is the scope for cheap local symbols. It lasts from one non
828 local symbol to the next one, without any provisions made by the programmer.
829 All other scopes differ in usage but use the same concept internally.
832 <sect1>Generic nested scopes<p>
834 A nested scoped for generic use is started with <tt/<ref id=".SCOPE"
835 name=".SCOPE">/ and closed with <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/.
836 The scope can have a name, in which case it is accessible from the outside by
837 using <ref id="scopesyntax" name="explicit scopes">. If the scope does not
838 have a name, all symbols created within the scope are local to the scope, and
839 aren't accessible from the outside.
841 A nested scope can access symbols from the local or from enclosing scopes by
842 name without using explicit scope names. In some cases there may be
843 ambiguities, for example if there is a reference to a local symbol that is not
844 yet defined, but a symbol with the same name exists in outer scopes:
856 In the example above, the <tt/lda/ instruction will load the value 3 into the
857 accumulator, because <tt/foo/ is redefined in the scope. However:
869 Here, <tt/lda/ will still load from <tt/$12,x/, but since it is unknown to the
870 assembler that <tt/foo/ is a zeropage symbol when translating the instruction,
871 absolute mode is used instead. In fact, the assembler will not use absolute
872 mode by default, but it will search through the enclosing scopes for a symbol
873 with the given name. If one is found, the address size of this symbol is used.
874 This may lead to errors:
886 In this case, when the assembler sees the symbol <tt/foo/ in the <tt/lda/
887 instruction, it will search for an already defined symbol <tt/foo/. It will
888 find <tt/foo/ in scope <tt/outer/, and a close look reveals that it is a
889 zeropage symbol. So the assembler will use zeropage addressing mode. If
890 <tt/foo/ is redefined later in scope <tt/inner/, the assembler tries to change
891 the address in the <tt/lda/ instruction already translated, but since the new
892 value needs absolute addressing mode, this fails, and an error message "Range
895 Of course the most simple solution for the problem is to move the definition
896 of <tt/foo/ in scope <tt/inner/ upwards, so it precedes its use. There may be
897 rare cases when this cannot be done. In these cases, you can use one of the
898 address size override operators:
910 This will cause the <tt/lda/ instruction to be translated using absolute
911 addressing mode, which means changing the symbol reference later does not
915 <sect1>Nested procedures<p>
917 A nested procedure is created by use of <tt/<ref id=".PROC" name=".PROC">/. It
918 differs from a <tt/<ref id=".SCOPE" name=".SCOPE">/ in that it must have a
919 name, and a it will introduce a symbol with this name in the enclosing scope.
928 is actually the same as
937 This is the reason why a procedure must have a name. If you want a scope
938 without a name, use <tt/<ref id=".SCOPE" name=".SCOPE">/.
940 <bf/Note:/ As you can see from the example above, scopes and symbols live in
941 different namespaces. There can be a symbol named <tt/foo/ and a scope named
942 <tt/foo/ without any conflicts (but see the section titled <ref
943 id="scopesearch" name=""Scope search order"">).
946 <sect1>Structs, unions and enums<p>
948 Structs, unions and enums are explained in a <ref id="structs" name="separate
949 section">, I do only cover them here, because if they are declared with a
950 name, they open a nested scope, similar to <tt/<ref id=".SCOPE"
951 name=".SCOPE">/. However, when no name is specified, the behaviour is
952 different: In this case, no new scope will be opened, symbols declared within
953 a struct, union, or enum declaration will then be added to the enclosing scope
957 <sect1>Explicit scope specification<label id="scopesyntax"><p>
959 Accessing symbols from other scopes is possible by using an explicit scope
960 specification, provided that the scope where the symbol lives in has a name.
961 The namespace token (<tt/::/) is used to access other scopes:
969 lda foo::bar ; Access foo in scope bar
972 The only way to deny access to a scope from the outside is to declare a scope
973 without a name (using the <tt/<ref id=".SCOPE" name=".SCOPE">/ command).
975 A special syntax is used to specify the global scope: If a symbol or scope is
976 preceded by the namespace token, the global scope is searched:
983 lda #::bar ; Access the global bar (which is 3)
988 <sect1>Scope search order<label id="scopesearch"><p>
990 The assembler searches for a scope in a similar way as for a symbol. First, it
991 looks in the current scope, and then it walks up the enclosing scopes until
994 However, one important thing to note when using explicit scope syntax is, that
995 a symbol may be accessed before it is defined, but a scope may <bf/not/ be
996 used without a preceding definition. This means that in the following
1005 lda #foo::bar ; Will load 3, not 2!
1012 the reference to the scope <tt/foo/ will use the global scope, and not the
1013 local one, because the local one is not visible at the point where it is
1016 Things get more complex if a complete chain of scopes is specified:
1027 lda #outer::inner::bar ; 1
1039 When <tt/outer::inner::bar/ is referenced in the <tt/lda/ instruction, the
1040 assembler will first search in the local scope for a scope named <tt/outer/.
1041 Since none is found, the enclosing scope (<tt/another/) is checked. There is
1042 still no scope named <tt/outer/, so scope <tt/foo/ is checked, and finally
1043 scope <tt/outer/ is found. Within this scope, <tt/inner/ is searched, and in
1044 this scope, the assembler looks for a symbol named <tt/bar/.
1046 Please note that once the anchor scope is found, all following scopes
1047 (<tt/inner/ in this case) are expected to be found exactly in this scope. The
1048 assembler will search the scope tree only for the first scope (if it is not
1049 anchored in the root scope). Starting from there on, there is no flexibility,
1050 so if the scope named <tt/outer/ found by the assembler does not contain a
1051 scope named <tt/inner/, this would be an error, even if such a pair does exist
1052 (one level up in global scope).
1054 Ambiguities that may be introduced by this search algorithm may be removed by
1055 anchoring the scope specification in the global scope. In the example above,
1056 if you want to access the "other" symbol <tt/bar/, you would have to write:
1067 lda #::outer::inner::bar ; 2
1080 <sect>Address sizes and memory models<label id="address-sizes"><p>
1082 <sect1>Address sizes<p>
1084 ca65 assigns each segment and each symbol an address size. This is true, even
1085 if the symbol is not used as an address. You may also think of a value range
1086 of the symbol instead of an address size.
1088 Possible address sizes are:
1091 <item>Zeropage or direct (8 bits)
1092 <item>Absolute (16 bits)
1094 <item>Long (32 bits)
1097 Since the assembler uses default address sizes for the segments and symbols,
1098 it is usually not necessary to override the default behaviour. In cases, where
1099 it is necessary, the following keywords may be used to specify address sizes:
1102 <item>DIRECT, ZEROPAGE or ZP for zeropage addressing (8 bits).
1103 <item>ABSOLUTE, ABS or NEAR for absolute addressing (16 bits).
1104 <item>FAR for far addressing (24 bits).
1105 <item>LONG or DWORD for long addressing (32 bits).
1109 <sect1>Address sizes of segments<p>
1111 The assembler assigns an address size to each segment. Since the
1112 representation of a label within this segment is "segment start + offset",
1113 labels will inherit the address size of the segment they are declared in.
1115 The address size of a segment may be changed, by using an optional address
1116 size modifier. See the <tt/<ref id=".SEGMENT" name="segment directive">/ for
1117 an explanation on how this is done.
1120 <sect1>Address sizes of symbols<p>
1125 <sect1>Memory models<p>
1127 The default address size of a segment depends on the memory model used. Since
1128 labels inherit the address size from the segment they are declared in,
1129 changing the memory model is an easy way to change the address size of many
1135 <sect>Pseudo variables<label id="pseudo-variables"><p>
1137 Pseudo variables are readable in all cases, and in some special cases also
1140 <sect1><tt>*</tt><p>
1142 Reading this pseudo variable will return the program counter at the start
1143 of the current input line.
1145 Assignment to this variable is possible when <tt/<ref id=".FEATURE"
1146 name=".FEATURE pc_assignment">/ is used. Note: You should not use
1147 assignments to <tt/*/, use <tt/<ref id=".ORG" name=".ORG">/ instead.
1150 <sect1><tt>.CPU</tt><label id=".CPU"><p>
1152 Reading this pseudo variable will give a constant integer value that
1153 tells which CPU is currently enabled. It can also tell which instruction
1154 set the CPU is able to translate. The value read from the pseudo variable
1155 should be further examined by using one of the constants defined by the
1156 "cpu" macro package (see <tt/<ref id=".MACPACK" name=".MACPACK">/).
1158 It may be used to replace the .IFPxx pseudo instructions or to construct
1159 even more complex expressions.
1165 .if (.cpu .bitand CPU_ISET_65816)
1177 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
1179 This builtin pseudo variable is only available in macros. It is replaced by
1180 the actual number of parameters that were given in the macro invocation.
1185 .macro foo arg1, arg2, arg3
1186 .if .paramcount <> 3
1187 .error "Too few parameters for macro foo"
1193 See section <ref id="macros" name="Macros">.
1196 <sect1><tt>.TIME</tt><label id=".TIME"><p>
1198 Reading this pseudo variable will give a constant integer value that
1199 represents the current time in POSIX standard (as seconds since the
1202 It may be used to encode the time of translation somewhere in the created
1208 .dword .time ; Place time here
1212 <sect1><tt>.VERSION</tt><label id=".VERSION"><p>
1214 Reading this pseudo variable will give the assembler version according to
1215 the following formula:
1217 VER_MAJOR*$100 + VER_MINOR*$10 + VER_PATCH
1219 It may be used to encode the assembler version or check the assembler for
1220 special features not available with older versions.
1224 Version 2.11.1 of the assembler will return $2B1 as numerical constant when
1225 reading the pseudo variable <tt/.VERSION/.
1229 <sect>Pseudo functions<label id="pseudo-functions"><p>
1231 Pseudo functions expect their arguments in parenthesis, and they have a result,
1232 either a string or an expression.
1235 <sect1><tt>.BANKBYTE</tt><label id=".BANKBYTE"><p>
1237 The function returns the bank byte (that is, bits 16-23) of its argument.
1238 It works identical to the '^' operator.
1240 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1241 <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>
1244 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
1246 Builtin function. The function evaluates its argument in braces and yields
1247 "false" if the argument is non blank (there is an argument), and "true" if
1248 there is no argument. The token list that makes up the function argument
1249 may optionally be enclosed in curly braces. This allows the inclusion of
1250 tokens that would otherwise terminate the list (the closing right
1251 parenthesis). The curly braces are not considered part of the list, a list
1252 just consisting of curly braces is considered to be empty.
1254 As an example, the <tt/.IFBLANK/ statement may be replaced by
1262 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
1264 Builtin string function. The function allows to concatenate a list of string
1265 constants separated by commas. The result is a string constant that is the
1266 concatenation of all arguments. This function is most useful in macros and
1267 when used together with the <tt/.STRING/ builtin function. The function may
1268 be used in any case where a string constant is expected.
1273 .include .concat ("myheader", ".", "inc")
1276 This is the same as the command
1279 .include "myheader.inc"
1283 <sect1><tt>.CONST</tt><label id=".CONST"><p>
1285 Builtin function. The function evaluates its argument in braces and
1286 yields "true" if the argument is a constant expression (that is, an
1287 expression that yields a constant value at assembly time) and "false"
1288 otherwise. As an example, the .IFCONST statement may be replaced by
1295 <sect1><tt>.HIBYTE</tt><label id=".HIBYTE"><p>
1297 The function returns the high byte (that is, bits 8-15) of its argument.
1298 It works identical to the '>' operator.
1300 See: <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>,
1301 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1304 <sect1><tt>.HIWORD</tt><label id=".HIWORD"><p>
1306 The function returns the high word (that is, bits 16-31) of its argument.
1308 See: <tt><ref id=".LOWORD" name=".LOWORD"></tt>
1311 <sect1><tt>.IDENT</tt><label id=".IDENT"><p>
1313 The function expects a string as its argument, and converts this argument
1314 into an identifier. If the string starts with the current <tt/<ref
1315 id=".LOCALCHAR" name=".LOCALCHAR">/, it will be converted into a cheap local
1316 identifier, otherwise it will be converted into a normal identifier.
1321 .macro makelabel arg1, arg2
1322 .ident (.concat (arg1, arg2)):
1325 makelabel "foo", "bar"
1327 .word foobar ; Valid label
1331 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1333 Builtin function. Extracts the left part of a given token list.
1338 .LEFT (<int expr>, <token list>)
1341 The first integer expression gives the number of tokens to extract from
1342 the token list. The second argument is the token list itself. The token
1343 list may optionally be enclosed into curly braces. This allows the
1344 inclusion of tokens that would otherwise terminate the list (the closing
1345 right paren in the given case).
1349 To check in a macro if the given argument has a '#' as first token
1350 (immediate addressing mode), use something like this:
1355 .if (.match (.left (1, {arg}), #))
1357 ; ldax called with immediate operand
1365 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1366 name=".RIGHT"></tt> builtin functions.
1369 <sect1><tt>.LOBYTE</tt><label id=".LOBYTE"><p>
1371 The function returns the low byte (that is, bits 0-7) of its argument.
1372 It works identical to the '<' operator.
1374 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1375 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1378 <sect1><tt>.LOWORD</tt><label id=".LOWORD"><p>
1380 The function returns the low word (that is, bits 0-15) of its argument.
1382 See: <tt><ref id=".HIWORD" name=".HIWORD"></tt>
1385 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1387 Builtin function. Matches two token lists against each other. This is
1388 most useful within macros, since macros are not stored as strings, but
1394 .MATCH(<token list #1>, <token list #2>)
1397 Both token list may contain arbitrary tokens with the exception of the
1398 terminator token (comma resp. right parenthesis) and
1405 The token lists may optionally be enclosed into curly braces. This allows
1406 the inclusion of tokens that would otherwise terminate the list (the closing
1407 right paren in the given case). Often a macro parameter is used for any of
1410 Please note that the function does only compare tokens, not token
1411 attributes. So any number is equal to any other number, regardless of the
1412 actual value. The same is true for strings. If you need to compare tokens
1413 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1414 name=".XMATCH"></tt> function.
1418 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1419 while honoring the sign bit. The builtin processor instructions will allow
1420 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1421 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1422 to check for this and print and error for invalid calls.
1427 .if (.not .blank(arg)) .and (.not .match ({arg}, a))
1428 .error "Syntax error"
1431 cmp #$80 ; Bit 7 into carry
1432 lsr a ; Shift carry into bit 7
1437 The macro will only accept no arguments, or one argument that must be the
1438 reserved keyword "A".
1440 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1443 <sect1><tt>.MAX</tt><label id=".MAX"><p>
1445 Builtin function. The result is the larger of two values.
1450 .MAX (<value #1>, <value #2>)
1456 ; Reserve space for the larger of two data blocks
1457 savearea: .max (.sizeof (foo), .sizeof (bar))
1460 See: <tt><ref id=".MIN" name=".MIN"></tt>
1463 <sect1><tt>.MID</tt><label id=".MID"><p>
1465 Builtin function. Takes a starting index, a count and a token list as
1466 arguments. Will return part of the token list.
1471 .MID (<int expr>, <int expr>, <token list>)
1474 The first integer expression gives the starting token in the list (the first
1475 token has index 0). The second integer expression gives the number of tokens
1476 to extract from the token list. The third argument is the token list itself.
1477 The token list may optionally be enclosed into curly braces. This allows the
1478 inclusion of tokens that would otherwise terminate the list (the closing
1479 right paren in the given case).
1483 To check in a macro if the given argument has a '<tt/#/' as first token
1484 (immediate addressing mode), use something like this:
1489 .if (.match (.mid (0, 1, {arg}), #))
1491 ; ldax called with immediate operand
1499 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1500 name=".RIGHT"></tt> builtin functions.
1503 <sect1><tt>.MIN</tt><label id=".MIN"><p>
1505 Builtin function. The result is the smaller of two values.
1510 .MIN (<value #1>, <value #2>)
1516 ; Reserve space for some data, but 256 bytes minimum
1517 savearea: .min (.sizeof (foo), 256)
1520 See: <tt><ref id=".MAX" name=".MAX"></tt>
1523 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
1525 Builtin function. The function expects an identifier as argument in braces.
1526 The argument is evaluated, and the function yields "true" if the identifier
1527 is a symbol that has already been referenced somewhere in the source file up
1528 to the current position. Otherwise the function yields false. As an example,
1529 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
1535 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1538 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
1540 Builtin function. Extracts the right part of a given token list.
1545 .RIGHT (<int expr>, <token list>)
1548 The first integer expression gives the number of tokens to extract from the
1549 token list. The second argument is the token list itself. The token list
1550 may optionally be enclosed into curly braces. This allows the inclusion of
1551 tokens that would otherwise terminate the list (the closing right paren in
1554 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
1555 name=".MID"></tt> builtin functions.
1558 <sect1><tt>.SIZEOF</tt><label id=".SIZEOF"><p>
1560 <tt/.SIZEOF/ is a pseudo function that returns the size of its argument. The
1561 argument can be a struct/union, a struct member, a procedure, or a label. In
1562 case of a procedure or label, its size is defined by the amount of data
1563 placed in the segment where the label is relative to. If a line of code
1564 switches segments (for example in a macro) data placed in other segments
1565 does not count for the size.
1567 Please note that a symbol or scope must exist, before it is used together with
1568 <tt/.SIZEOF/ (this may get relaxed later, but will always be true for scopes).
1569 A scope has preference over a symbol with the same name, so if the last part
1570 of a name represents both, a scope and a symbol, the scope is chosen over the
1573 After the following code:
1576 .struct Point ; Struct size = 4
1581 P: .tag Point ; Declare a point
1582 @P: .tag Point ; Declare another point
1594 .data ; Segment switch!!!
1600 <tag><tt/.sizeof(Point)/</tag>
1601 will have the value 4, because this is the size of struct <tt/Point/.
1603 <tag><tt/.sizeof(Point::xcoord)/</tag>
1604 will have the value 2, because this is the size of the member <tt/xcoord/
1605 in struct <tt/Point/.
1607 <tag><tt/.sizeof(P)/</tag>
1608 will have the value 4, this is the size of the data declared on the same
1609 source line as the label <tt/P/, which is in the same segment that <tt/P/
1612 <tag><tt/.sizeof(@P)/</tag>
1613 will have the value 4, see above. The example demonstrates that <tt/.SIZEOF/
1614 does also work for cheap local symbols.
1616 <tag><tt/.sizeof(Code)/</tag>
1617 will have the value 3, since this is amount of data emitted into the code
1618 segment, the segment that was active when <tt/Code/ was entered. Note that
1619 this value includes the amount of data emitted in child scopes (in this
1620 case <tt/Code::Inner/).
1622 <tag><tt/.sizeof(Code::Inner)/</tag>
1623 will have the value 1 as expected.
1625 <tag><tt/.sizeof(Data)/</tag>
1626 will have the value 0. Data is emitted within the scope <tt/Data/, but since
1627 the segment is switched after entry, this data is emitted into another
1632 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
1634 Builtin function. The function accepts a string and an index as
1635 arguments and returns the value of the character at the given position
1636 as an integer value. The index is zero based.
1642 ; Check if the argument string starts with '#'
1643 .if (.strat (Arg, 0) = '#')
1650 <sect1><tt>.SPRINTF</tt><label id=".SPRINTF"><p>
1652 Builtin function. It expects a format string as first argument. The number
1653 and type of the following arguments depend on the format string. The format
1654 string is similar to the one of the C <tt/printf/ function. Missing things
1655 are: Length modifiers, variable width.
1657 The result of the function is a string.
1664 ; Generate an identifier:
1665 .ident (.sprintf ("%s%03d", "label", num)):
1669 <sect1><tt>.STRING</tt><label id=".STRING"><p>
1671 Builtin function. The function accepts an argument in braces and converts
1672 this argument into a string constant. The argument may be an identifier, or
1673 a constant numeric value.
1675 Since you can use a string in the first place, the use of the function may
1676 not be obvious. However, it is useful in macros, or more complex setups.
1681 ; Emulate other assemblers:
1683 .segment .string(name)
1688 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
1690 Builtin function. The function accepts a string argument in braces and
1691 evaluates to the length of the string.
1695 The following macro encodes a string as a pascal style string with
1696 a leading length byte.
1700 .byte .strlen(Arg), Arg
1705 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
1707 Builtin function. The function accepts a token list in braces. The function
1708 result is the number of tokens given as argument. The token list may
1709 optionally be enclosed into curly braces which are not considered part of
1710 the list and not counted. Enclosement in curly braces allows the inclusion
1711 of tokens that would otherwise terminate the list (the closing right paren
1716 The <tt/ldax/ macro accepts the '#' token to denote immediate addressing (as
1717 with the normal 6502 instructions). To translate it into two separate 8 bit
1718 load instructions, the '#' token has to get stripped from the argument:
1722 .if (.match (.mid (0, 1, {arg}), #))
1723 ; ldax called with immediate operand
1724 lda #<(.right (.tcount ({arg})-1, {arg}))
1725 ldx #>(.right (.tcount ({arg})-1, {arg}))
1733 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
1735 Builtin function. Matches two token lists against each other. This is
1736 most useful within macros, since macros are not stored as strings, but
1742 .XMATCH(<token list #1>, <token list #2>)
1745 Both token list may contain arbitrary tokens with the exception of the
1746 terminator token (comma resp. right parenthesis) and
1753 The token lists may optionally be enclosed into curly braces. This allows
1754 the inclusion of tokens that would otherwise terminate the list (the closing
1755 right paren in the given case). Often a macro parameter is used for any of
1758 The function compares tokens <em/and/ token values. If you need a function
1759 that just compares the type of tokens, have a look at the <tt><ref
1760 id=".MATCH" name=".MATCH"></tt> function.
1762 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
1766 <sect>Control commands<label id="control-commands"><p>
1768 Here's a list of all control commands and a description, what they do:
1771 <sect1><tt>.A16</tt><label id=".A16"><p>
1773 Valid only in 65816 mode. Switch the accumulator to 16 bit.
1775 Note: This command will not emit any code, it will tell the assembler to
1776 create 16 bit operands for immediate accumulator addressing mode.
1778 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1781 <sect1><tt>.A8</tt><label id=".A8"><p>
1783 Valid only in 65816 mode. Switch the accumulator to 8 bit.
1785 Note: This command will not emit any code, it will tell the assembler to
1786 create 8 bit operands for immediate accu addressing mode.
1788 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1791 <sect1><tt>.ADDR</tt><label id=".ADDR"><p>
1793 Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and
1794 may be used for better readability if the data words are address values. In
1795 65816 mode, the address is forced to be 16 bit wide to fit into the current
1796 segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command
1797 must be followed by a sequence of (not necessarily constant) expressions.
1802 .addr $0D00, $AF13, _Clear
1805 See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD"
1809 <sect1><tt>.ALIGN</tt><label id=".ALIGN"><p>
1811 Align data to a given boundary. The command expects a constant integer
1812 argument that must be a power of two, plus an optional second argument
1813 in byte range. If there is a second argument, it is used as fill value,
1814 otherwise the value defined in the linker configuration file is used
1815 (the default for this value is zero).
1817 Since alignment depends on the base address of the module, you must
1818 give the same (or a greater) alignment for the segment when linking.
1819 The linker will give you a warning, if you don't do that.
1828 <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"><p>
1830 Define a string with a trailing zero.
1835 Msg: .asciiz "Hello world"
1838 This will put the string "Hello world" followed by a binary zero into
1839 the current segment. There may be more strings separated by commas, but
1840 the binary zero is only appended once (after the last one).
1843 <sect1><tt>.ASSERT</tt><label id=".ASSERT"><p>
1845 Add an assertion. The command is followed by an expression, an action
1846 specifier, and an optional message that is output in case the assertion
1847 fails. If no message was given, the string "Assertion failed" is used. The
1848 action specifier may be one of <tt/warning/, <tt/error/, <tt/ldwarning/ or
1849 <tt/lderror/. In the former two cases, the assertion is evaluated by the
1850 assembler if possible, and in any case, it's also passed to the linker in
1851 the object file (if one is generated). The linker will then evaluate the
1852 expression when segment placement has been done.
1857 .assert * = $8000, error, "Code not at $8000"
1860 The example assertion will check that the current location is at $8000,
1861 when the output file is written, and abort with an error if this is not
1862 the case. More complex expressions are possible. The action specifier
1863 <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs
1864 an error message. In the latter case, generation of the output file is
1865 suppressed in both the assembler and linker.
1868 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
1870 Is followed by a plus or a minus character. When switched on (using a
1871 +), undefined symbols are automatically marked as import instead of
1872 giving errors. When switched off (which is the default so this does not
1873 make much sense), this does not happen and an error message is
1874 displayed. The state of the autoimport flag is evaluated when the
1875 complete source was translated, before outputting actual code, so it is
1876 <em/not/ possible to switch this feature on or off for separate sections
1877 of code. The last setting is used for all symbols.
1879 You should probably not use this switch because it delays error
1880 messages about undefined symbols until the link stage. The cc65
1881 compiler (which is supposed to produce correct assembler code in all
1882 circumstances, something which is not true for most assembler
1883 programmers) will insert this command to avoid importing each and every
1884 routine from the runtime library.
1889 .autoimport + ; Switch on auto import
1892 <sect1><tt>.BANKBYTES</tt><label id=".BANKBYTES"><p>
1894 Define byte sized data by extracting only the bank byte (that is, bits 16-23) from
1895 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
1896 the operator '^' prepended to each expression in its list.
1901 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
1903 TableLookupLo: .lobytes MyTable
1904 TableLookupHi: .hibytes MyTable
1905 TableLookupBank: .bankbytes MyTable
1908 which is equivalent to
1911 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
1912 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
1913 TableLookupBank: .byte ^TableItem0, ^TableItem1, ^TableItem2, ^TableItem3
1916 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
1917 <tt><ref id=".HIBYTES" name=".HIBYTES"></tt>,
1918 <tt><ref id=".LOBYTES" name=".LOBYTES"></tt>
1921 <sect1><tt>.BSS</tt><label id=".BSS"><p>
1923 Switch to the BSS segment. The name of the BSS segment is always "BSS",
1924 so this is a shortcut for
1930 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1933 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
1935 Define byte sized data. Must be followed by a sequence of (byte ranged)
1936 expressions or strings.
1942 .byt "world", $0D, $00
1946 <sect1><tt>.CASE</tt><label id=".CASE"><p>
1948 Switch on or off case sensitivity on identifiers. The default is off
1949 (that is, identifiers are case sensitive), but may be changed by the
1950 -i switch on the command line.
1951 The command must be followed by a '+' or '-' character to switch the
1952 option on or off respectively.
1957 .case - ; Identifiers are not case sensitive
1961 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
1963 Apply a custom mapping for characters. The command is followed by two
1964 numbers in the range 1..255. The first one is the index of the source
1965 character, the second one is the mapping. The mapping applies to all
1966 character and string constants when they generate output, and overrides
1967 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
1968 command line switch.
1973 .charmap $41, $61 ; Map 'A' to 'a'
1977 <sect1><tt>.CODE</tt><label id=".CODE"><p>
1979 Switch to the CODE segment. The name of the CODE segment is always
1980 "CODE", so this is a shortcut for
1986 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1989 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
1991 Export a symbol and mark it in a special way. The linker is able to build
1992 tables of all such symbols. This may be used to automatically create a list
1993 of functions needed to initialize linked library modules.
1995 Note: The linker has a feature to build a table of marked routines, but it
1996 is your code that must call these routines, so just declaring a symbol with
1997 <tt/.CONDES/ does nothing by itself.
1999 All symbols are exported as an absolute (16 bit) symbol. You don't need to
2000 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
2001 is implied by <tt/.CONDES/.
2003 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
2004 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
2005 specifying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
2006 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
2007 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
2008 name=".INTERRUPTOR"></tt> commands are actually shortcuts for <tt/.CONDES/
2009 with a type of <tt/constructor/ resp. <tt/destructor/ or <tt/interruptor/.
2011 After the type, an optional priority may be specified. Higher numeric values
2012 mean higher priority. If no priority is given, the default priority of 7 is
2013 used. Be careful when assigning priorities to your own module constructors
2014 so they won't interfere with the ones in the cc65 library.
2019 .condes ModuleInit, constructor
2020 .condes ModInit, 0, 16
2023 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
2024 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
2025 name=".INTERRUPTOR"></tt> commands and the separate section <ref id="condes"
2026 name="Module constructors/destructors"> explaining the feature in more
2030 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
2032 Export a symbol and mark it as a module constructor. This may be used
2033 together with the linker to build a table of constructor subroutines that
2034 are called by the startup code.
2036 Note: The linker has a feature to build a table of marked routines, but it
2037 is your code that must call these routines, so just declaring a symbol as
2038 constructor does nothing by itself.
2040 A constructor is always exported as an absolute (16 bit) symbol. You don't
2041 need to use an additional <tt/.export/ statement, this is implied by
2042 <tt/.constructor/. It may have an optional priority that is separated by a
2043 comma. Higher numeric values mean a higher priority. If no priority is
2044 given, the default priority of 7 is used. Be careful when assigning
2045 priorities to your own module constructors so they won't interfere with the
2046 ones in the cc65 library.
2051 .constructor ModuleInit
2052 .constructor ModInit, 16
2055 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
2056 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
2057 <ref id="condes" name="Module constructors/destructors"> explaining the
2058 feature in more detail.
2061 <sect1><tt>.DATA</tt><label id=".DATA"><p>
2063 Switch to the DATA segment. The name of the DATA segment is always
2064 "DATA", so this is a shortcut for
2070 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2073 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
2075 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
2076 create word sized data in native 65XX format). Must be followed by a
2077 sequence of (word ranged) expressions.
2085 This will emit the bytes
2091 into the current segment in that order.
2094 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
2096 Switch on or off debug info generation. The default is off (that is,
2097 the object file will not contain debug infos), but may be changed by the
2098 -g switch on the command line.
2099 The command must be followed by a '+' or '-' character to switch the
2100 option on or off respectively.
2105 .debuginfo + ; Generate debug info
2109 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
2111 Start a define style macro definition. The command is followed by an
2112 identifier (the macro name) and optionally by a list of formal arguments
2114 See section <ref id="macros" name="Macros">.
2117 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
2119 Builtin function. The function expects an identifier as argument in braces.
2120 The argument is evaluated, and the function yields "true" if the identifier
2121 is a symbol that is already defined somewhere in the source file up to the
2122 current position. Otherwise the function yields false. As an example, the
2123 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
2130 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
2132 Export a symbol and mark it as a module destructor. This may be used
2133 together with the linker to build a table of destructor subroutines that
2134 are called by the startup code.
2136 Note: The linker has a feature to build a table of marked routines, but it
2137 is your code that must call these routines, so just declaring a symbol as
2138 constructor does nothing by itself.
2140 A destructor is always exported as an absolute (16 bit) symbol. You don't
2141 need to use an additional <tt/.export/ statement, this is implied by
2142 <tt/.destructor/. It may have an optional priority that is separated by a
2143 comma. Higher numerical values mean a higher priority. If no priority is
2144 given, the default priority of 7 is used. Be careful when assigning
2145 priorities to your own module destructors so they won't interfere with the
2146 ones in the cc65 library.
2151 .destructor ModuleDone
2152 .destructor ModDone, 16
2155 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
2156 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
2157 section <ref id="condes" name="Module constructors/destructors"> explaining
2158 the feature in more detail.
2161 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
2163 Define dword sized data (4 bytes) Must be followed by a sequence of
2169 .dword $12344512, $12FA489
2173 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
2175 Conditional assembly: Reverse the current condition.
2178 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
2180 Conditional assembly: Reverse current condition and test a new one.
2183 <sect1><tt>.END</tt><label id=".END"><p>
2185 Forced end of assembly. Assembly stops at this point, even if the command
2186 is read from an include file.
2189 <sect1><tt>.ENDENUM</tt><label id=".ENDENUM"><p>
2191 End a <tt><ref id=".ENUM" name=".ENUM"></tt> declaration.
2194 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
2196 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
2197 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
2200 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
2202 End of macro definition (see section <ref id="macros" name="Macros">).
2205 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
2207 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
2210 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
2212 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
2215 <sect1><tt>.ENDSCOPE</tt><label id=".ENDSCOPE"><p>
2217 End of local lexical level (see <tt/<ref id=".SCOPE" name=".SCOPE">/).
2220 <sect1><tt>.ENDSTRUCT</tt><label id=".ENDSTRUCT"><p>
2222 Ends a struct definition. See the <tt/<ref id=".STRUCT" name=".STRUCT">/
2223 command and the separate section named <ref id="structs" name=""Structs
2227 <sect1><tt>.ENUM</tt><label id=".ENUM"><p>
2229 Start an enumeration. This directive is very similar to the C <tt/enum/
2230 keyword. If a name is given, a new scope is created for the enumeration,
2231 otherwise the enumeration members are placed in the enclosing scope.
2233 In the enumeration body, symbols are declared. The first symbol has a value
2234 of zero, and each following symbol will get the value of the preceding plus
2235 one. This behaviour may be overridden by an explicit assignment. Two symbols
2236 may have the same value.
2248 Above example will create a new scope named <tt/errorcodes/ with three
2249 symbols in it that get the values 0, 1 and 2 respectively. Another way
2250 to write this would have been:
2260 Please note that explicit scoping must be used to access the identifiers:
2263 .word errorcodes::no_error
2266 A more complex example:
2275 EWOULDBLOCK = EAGAIN
2279 In this example, the enumeration does not have a name, which means that the
2280 members will be visible in the enclosing scope and can be used in this scope
2281 without explicit scoping. The first member (<tt/EUNKNOWN/) has the value -1.
2282 The value for the following members is incremented by one, so <tt/EOK/ would
2283 be zero and so on. <tt/EWOULDBLOCK/ is an alias for <tt/EGAIN/, so it has an
2284 override for the value using an already defined symbol.
2287 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
2289 Force an assembly error. The assembler will output an error message
2290 preceded by "User error" and will <em/not/ produce an object file.
2292 This command may be used to check for initial conditions that must be
2293 set before assembling a source file.
2303 .error "Must define foo or bar!"
2307 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
2308 id=".OUT" name=".OUT"></tt> directives.
2311 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
2313 Abort a macro expansion immediately. This command is often useful in
2314 recursive macros. See separate section <ref id="macros" name="Macros">.
2317 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
2319 Make symbols accessible from other modules. Must be followed by a comma
2320 separated list of symbols to export, with each one optionally followed by an
2321 address specification and (also optional) an assignment. Using an additional
2322 assignment in the export statement allows to define and export a symbol in
2323 one statement. The default is to export the symbol with the address size it
2324 actually has. The assembler will issue a warning, if the symbol is exported
2325 with an address size smaller than the actual address size.
2332 .export foobar: far = foo * bar
2333 .export baz := foobar, zap: far = baz - bar
2336 As with constant definitions, using <tt/:=/ instead of <tt/=/ marks the
2339 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
2342 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
2344 Make symbols accessible from other modules. Must be followed by a comma
2345 separated list of symbols to export. The exported symbols are explicitly
2346 marked as zero page symbols. An assignment may be included in the
2347 <tt/.EXPORTZP/ statement. This allows to define and export a symbol in one
2354 .exportzp baz := $02
2357 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
2360 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
2362 Define far (24 bit) address data. The command must be followed by a
2363 sequence of (not necessarily constant) expressions.
2368 .faraddr DrawCircle, DrawRectangle, DrawHexagon
2371 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
2374 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
2376 This directive may be used to enable one or more compatibility features
2377 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
2378 possible, it may be useful when porting sources written for other
2379 assemblers. There is no way to switch a feature off, once you have
2380 enabled it, so using
2386 will enable the feature until end of assembly is reached.
2388 The following features are available:
2392 <tag><tt>at_in_identifiers</tt><label id="at_in_identifiers"></tag>
2394 Accept the at character (`@') as a valid character in identifiers. The
2395 at character is not allowed to start an identifier, even with this
2398 <tag><tt>c_comments</tt></tag>
2400 Allow C like comments using <tt>/*</tt> and <tt>*/</tt> as left and right
2401 comment terminators. Note that C comments may not be nested. There's also a
2402 pitfall when using C like comments: All statements must be terminated by
2403 "end-of-line". Using C like comments, it is possible to hide the newline,
2404 which results in error messages. See the following non working example:
2407 lda #$00 /* This comment hides the newline
2411 <tag><tt>dollar_in_identifiers</tt><label id="dollar_in_identifiers"></tag>
2413 Accept the dollar sign (`$') as a valid character in identifiers. The
2414 dollar character is not allowed to start an identifier, even with this
2417 <tag><tt>dollar_is_pc</tt></tag>
2419 The dollar sign may be used as an alias for the star (`*'), which
2420 gives the value of the current PC in expressions.
2421 Note: Assignment to the pseudo variable is not allowed.
2423 <tag><tt>labels_without_colons</tt></tag>
2425 Allow labels without a trailing colon. These labels are only accepted,
2426 if they start at the beginning of a line (no leading white space).
2428 <tag><tt>leading_dot_in_identifiers</tt><label id="leading_dot_in_identifiers"></tag>
2430 Accept the dot (`.') as the first character of an identifier. This may be
2431 used for example to create macro names that start with a dot emulating
2432 control directives of other assemblers. Note however, that none of the
2433 reserved keywords built into the assembler, that starts with a dot, may be
2434 overridden. When using this feature, you may also get into trouble if
2435 later versions of the assembler define new keywords starting with a dot.
2437 <tag><tt>loose_char_term</tt></tag>
2439 Accept single quotes as well as double quotes as terminators for char
2442 <tag><tt>loose_string_term</tt></tag>
2444 Accept single quotes as well as double quotes as terminators for string
2447 <tag><tt>missing_char_term</tt></tag>
2449 Accept single quoted character constants where the terminating quote is
2454 <bf/Note:/ This does not work in conjunction with <tt/.FEATURE
2455 loose_string_term/, since in this case the input would be ambiguous.
2457 <tag><tt>org_per_seg</tt><label id="org_per_seg"></tag>
2459 This feature makes relocatable/absolute mode local to the current segment.
2460 Using <tt><ref id=".ORG" name=".ORG"></tt> when <tt/org_per_seg/ is in
2461 effect will only enable absolute mode for the current segment. Dito for
2462 <tt><ref id=".RELOC" name=".RELOC"></tt>.
2464 <tag><tt>pc_assignment</tt></tag>
2466 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
2467 is enabled). Such an assignment is handled identical to the <tt><ref
2468 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
2469 removing the lines with the assignments may also be an option when porting
2470 code written for older assemblers).
2472 <tag><tt>ubiquitous_idents</tt></tag>
2474 Allow the use of instructions names as names for macros and symbols. This
2475 makes it possible to "overload" instructions by defining a macro with the
2476 same name. This does also make it possible to introduce hard to find errors
2477 in your code, so be careful!
2481 It is also possible to specify features on the command line using the
2482 <tt><ref id="option--feature" name="--feature"></tt> command line option.
2483 This is useful when translating sources written for older assemblers, when
2484 you don't want to change the source code.
2486 As an example, to translate sources written for Andre Fachats xa65
2487 assembler, the features
2490 labels_without_colons, pc_assignment, loose_char_term
2493 may be helpful. They do not make ca65 completely compatible, so you may not
2494 be able to translate the sources without changes, even when enabling these
2495 features. However, I have found several sources that translate without
2496 problems when enabling these features on the command line.
2499 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
2501 Insert an option string into the object file. There are two forms of
2502 this command, one specifies the option by a keyword, the second
2503 specifies it as a number. Since usage of the second one needs knowledge
2504 of the internal encoding, its use is not recommended and I will only
2505 describe the first form here.
2507 The command is followed by one of the keywords
2515 a comma and a string. The option is written into the object file
2516 together with the string value. This is currently unidirectional and
2517 there is no way to actually use these options once they are in the
2523 .fileopt comment, "Code stolen from my brother"
2524 .fileopt compiler, "BASIC 2.0"
2525 .fopt author, "J. R. User"
2529 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
2531 Import an absolute symbol from another module. The command is followed by a
2532 comma separated list of symbols to import. The command is similar to <tt>
2533 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
2534 written to the generated object file, even if the symbol is never referenced
2535 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
2536 references for unused symbols).
2541 .forceimport needthisone, needthistoo
2544 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2547 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
2549 Declare symbols as global. Must be followed by a comma separated list of
2550 symbols to declare. Symbols from the list, that are defined somewhere in the
2551 source, are exported, all others are imported. Additional <tt><ref
2552 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
2553 name=".EXPORT"></tt> commands for the same symbol are allowed.
2562 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
2564 Declare symbols as global. Must be followed by a comma separated list of
2565 symbols to declare. Symbols from the list, that are defined somewhere in the
2566 source, are exported, all others are imported. Additional <tt><ref
2567 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
2568 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
2569 in the list are explicitly marked as zero page symbols.
2577 <sect1><tt>.HIBYTES</tt><label id=".HIBYTES"><p>
2579 Define byte sized data by extracting only the high byte (that is, bits 8-15) from
2580 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
2581 the operator '>' prepended to each expression in its list.
2586 .lobytes $1234, $2345, $3456, $4567
2587 .hibytes $fedc, $edcb, $dcba, $cba9
2590 which is equivalent to
2593 .byte $34, $45, $56, $67
2594 .byte $fe, $ed, $dc, $cb
2600 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
2602 TableLookupLo: .lobytes MyTable
2603 TableLookupHi: .hibytes MyTable
2606 which is equivalent to
2609 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
2610 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
2613 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
2614 <tt><ref id=".LOBYTES" name=".LOBYTES"></tt>,
2615 <tt><ref id=".BANKBYTES" name=".BANKBYTES"></tt>
2618 <sect1><tt>.I16</tt><label id=".I16"><p>
2620 Valid only in 65816 mode. Switch the index registers to 16 bit.
2622 Note: This command will not emit any code, it will tell the assembler to
2623 create 16 bit operands for immediate operands.
2625 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
2626 name=".SMART"></tt> commands.
2629 <sect1><tt>.I8</tt><label id=".I8"><p>
2631 Valid only in 65816 mode. Switch the index registers to 8 bit.
2633 Note: This command will not emit any code, it will tell the assembler to
2634 create 8 bit operands for immediate operands.
2636 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
2637 name=".SMART"></tt> commands.
2640 <sect1><tt>.IF</tt><label id=".IF"><p>
2642 Conditional assembly: Evaluate an expression and switch assembler output
2643 on or off depending on the expression. The expression must be a constant
2644 expression, that is, all operands must be defined.
2646 A expression value of zero evaluates to FALSE, any other value evaluates
2650 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
2652 Conditional assembly: Check if there are any remaining tokens in this line,
2653 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
2654 condition is not true, further lines are not assembled until an <tt><ref
2655 id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2656 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2658 This command is often used to check if a macro parameter was given. Since an
2659 empty macro parameter will evaluate to nothing, the condition will evaluate
2660 to FALSE if an empty parameter was given.
2674 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2677 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
2679 Conditional assembly: Evaluate an expression and switch assembler output
2680 on or off depending on the constness of the expression.
2682 A const expression evaluates to to TRUE, a non const expression (one
2683 containing an imported or currently undefined symbol) evaluates to
2686 See also: <tt><ref id=".CONST" name=".CONST"></tt>
2689 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
2691 Conditional assembly: Check if a symbol is defined. Must be followed by
2692 a symbol name. The condition is true if the the given symbol is already
2693 defined, and false otherwise.
2695 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2698 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
2700 Conditional assembly: Check if there are any remaining tokens in this line,
2701 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
2702 condition is not true, further lines are not assembled until an <tt><ref
2703 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2704 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2706 This command is often used to check if a macro parameter was given.
2707 Since an empty macro parameter will evaluate to nothing, the condition
2708 will evaluate to FALSE if an empty parameter was given.
2721 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2724 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
2726 Conditional assembly: Check if a symbol is defined. Must be followed by
2727 a symbol name. The condition is true if the the given symbol is not
2728 defined, and false otherwise.
2730 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2733 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
2735 Conditional assembly: Check if a symbol is referenced. Must be followed
2736 by a symbol name. The condition is true if if the the given symbol was
2737 not referenced before, and false otherwise.
2739 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2742 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
2744 Conditional assembly: Check if the assembler is currently in 6502 mode
2745 (see <tt><ref id=".P02" name=".P02"></tt> command).
2748 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
2750 Conditional assembly: Check if the assembler is currently in 65816 mode
2751 (see <tt><ref id=".P816" name=".P816"></tt> command).
2754 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
2756 Conditional assembly: Check if the assembler is currently in 65C02 mode
2757 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
2760 <sect1><tt>.IFPSC02</tt><label id=".IFPSC02"><p>
2762 Conditional assembly: Check if the assembler is currently in 65SC02 mode
2763 (see <tt><ref id=".PSC02" name=".PSC02"></tt> command).
2766 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
2768 Conditional assembly: Check if a symbol is referenced. Must be followed
2769 by a symbol name. The condition is true if if the the given symbol was
2770 referenced before, and false otherwise.
2772 This command may be used to build subroutine libraries in include files
2773 (you may use separate object modules for this purpose too).
2778 .ifref ToHex ; If someone used this subroutine
2779 ToHex: tay ; Define subroutine
2785 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2788 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
2790 Import a symbol from another module. The command is followed by a comma
2791 separated list of symbols to import, with each one optionally followed by
2792 an address specification.
2798 .import bar: zeropage
2801 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
2804 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
2806 Import a symbol from another module. The command is followed by a comma
2807 separated list of symbols to import. The symbols are explicitly imported
2808 as zero page symbols (that is, symbols with values in byte range).
2816 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2819 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
2821 Include a file as binary data. The command expects a string argument
2822 that is the name of a file to include literally in the current segment.
2823 In addition to that, a start offset and a size value may be specified,
2824 separated by commas. If no size is specified, all of the file from the
2825 start offset to end-of-file is used. If no start position is specified
2826 either, zero is assumed (which means that the whole file is inserted).
2831 ; Include whole file
2832 .incbin "sprites.dat"
2834 ; Include file starting at offset 256
2835 .incbin "music.dat", $100
2837 ; Read 100 bytes starting at offset 200
2838 .incbin "graphics.dat", 200, 100
2842 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
2844 Include another file. Include files may be nested up to a depth of 16.
2853 <sect1><tt>.INTERRUPTOR</tt><label id=".INTERRUPTOR"><p>
2855 Export a symbol and mark it as an interruptor. This may be used together
2856 with the linker to build a table of interruptor subroutines that are called
2859 Note: The linker has a feature to build a table of marked routines, but it
2860 is your code that must call these routines, so just declaring a symbol as
2861 interruptor does nothing by itself.
2863 An interruptor is always exported as an absolute (16 bit) symbol. You don't
2864 need to use an additional <tt/.export/ statement, this is implied by
2865 <tt/.interruptor/. It may have an optional priority that is separated by a
2866 comma. Higher numeric values mean a higher priority. If no priority is
2867 given, the default priority of 7 is used. Be careful when assigning
2868 priorities to your own module constructors so they won't interfere with the
2869 ones in the cc65 library.
2874 .interruptor IrqHandler
2875 .interruptor Handler, 16
2878 See the <tt><ref id=".CONDES" name=".CONDES"></tt> command and the separate
2879 section <ref id="condes" name="Module constructors/destructors"> explaining
2880 the feature in more detail.
2883 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
2885 Switch on or off line continuations using the backslash character
2886 before a newline. The option is off by default.
2887 Note: Line continuations do not work in a comment. A backslash at the
2888 end of a comment is treated as part of the comment and does not trigger
2890 The command must be followed by a '+' or '-' character to switch the
2891 option on or off respectively.
2896 .linecont + ; Allow line continuations
2899 #$20 ; This is legal now
2903 <sect1><tt>.LIST</tt><label id=".LIST"><p>
2905 Enable output to the listing. The command must be followed by a boolean
2906 switch ("on", "off", "+" or "-") and will enable or disable listing
2908 The option has no effect if the listing is not enabled by the command line
2909 switch -l. If -l is used, an internal counter is set to 1. Lines are output
2910 to the listing file, if the counter is greater than zero, and suppressed if
2911 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
2917 .list on ; Enable listing output
2921 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
2923 Set, how many bytes are shown in the listing for one source line. The
2924 default is 12, so the listing will show only the first 12 bytes for any
2925 source line that generates more than 12 bytes of code or data.
2926 The directive needs an argument, which is either "unlimited", or an
2927 integer constant in the range 4..255.
2932 .listbytes unlimited ; List all bytes
2933 .listbytes 12 ; List the first 12 bytes
2934 .incbin "data.bin" ; Include large binary file
2938 <sect1><tt>.LOBYTES</tt><label id=".LOBYTES"><p>
2940 Define byte sized data by extracting only the low byte (that is, bits 0-7) from
2941 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
2942 the operator '<' prepended to each expression in its list.
2947 .lobytes $1234, $2345, $3456, $4567
2948 .hibytes $fedc, $edcb, $dcba, $cba9
2951 which is equivalent to
2954 .byte $34, $45, $56, $67
2955 .byte $fe, $ed, $dc, $cb
2961 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
2963 TableLookupLo: .lobytes MyTable
2964 TableLookupHi: .hibytes MyTable
2967 which is equivalent to
2970 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
2971 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
2974 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
2975 <tt><ref id=".HIBYTES" name=".HIBYTES"></tt>,
2976 <tt><ref id=".BANKBYTES" name=".BANKBYTES"></tt>
2979 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
2981 This command may only be used inside a macro definition. It declares a
2982 list of identifiers as local to the macro expansion.
2984 A problem when using macros are labels: Since they don't change their name,
2985 you get a "duplicate symbol" error if the macro is expanded the second time.
2986 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
2987 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
2990 Some other assemblers start a new lexical block inside a macro expansion.
2991 This has some drawbacks however, since that will not allow <em/any/ symbol
2992 to be visible outside a macro, a feature that is sometimes useful. The
2993 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
2994 to address the problem.
2996 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
3000 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
3002 Defines the character that start "cheap" local labels. You may use one
3003 of '@' and '?' as start character. The default is '@'.
3005 Cheap local labels are labels that are visible only between two non
3006 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
3007 using explicit lexical nesting.
3014 Clear: lda #$00 ; Global label
3015 ?Loop: sta Mem,y ; Local label
3019 Sub: ... ; New global label
3020 bne ?Loop ; ERROR: Unknown identifier!
3024 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
3026 Insert a predefined macro package. The command is followed by an
3027 identifier specifying the macro package to insert. Available macro
3031 atari Defines the scrcode macro.
3032 cbm Defines the scrcode macro.
3033 cpu Defines constants for the .CPU variable.
3034 generic Defines generic macros like add and sub.
3035 longbranch Defines conditional long jump macros.
3038 Including a macro package twice, or including a macro package that
3039 redefines already existing macros will lead to an error.
3044 .macpack longbranch ; Include macro package
3046 cmp #$20 ; Set condition codes
3047 jne Label ; Jump long on condition
3050 Macro packages are explained in more detail in section <ref
3051 id="macropackages" name="Macro packages">.
3054 <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"><p>
3056 Start a classic macro definition. The command is followed by an identifier
3057 (the macro name) and optionally by a comma separated list of identifiers
3058 that are macro parameters.
3060 See section <ref id="macros" name="Macros">.
3063 <sect1><tt>.ORG</tt><label id=".ORG"><p>
3065 Start a section of absolute code. The command is followed by a constant
3066 expression that gives the new PC counter location for which the code is
3067 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
3070 By default, absolute/relocatable mode is global (valid even when switching
3071 segments). Using <tt>.FEATURE <ref id="org_per_seg" name="org_per_seg"></tt>
3072 it can be made segment local.
3074 Please note that you <em/do not need/ <tt/.ORG/ in most cases. Placing
3075 code at a specific address is the job of the linker, not the assembler, so
3076 there is usually no reason to assemble code to a specific address.
3081 .org $7FF ; Emit code starting at $7FF
3085 <sect1><tt>.OUT</tt><label id=".OUT"><p>
3087 Output a string to the console without producing an error. This command
3088 is similar to <tt/.ERROR/, however, it does not force an assembler error
3089 that prevents the creation of an object file.
3094 .out "This code was written by the codebuster(tm)"
3097 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
3098 id=".ERROR" name=".ERROR"></tt> directives.
3101 <sect1><tt>.P02</tt><label id=".P02"><p>
3103 Enable the 6502 instruction set, disable 65SC02, 65C02 and 65816
3104 instructions. This is the default if not overridden by the
3105 <tt><ref id="option--cpu" name="--cpu"></tt> command line option.
3107 See: <tt><ref id=".PC02" name=".PC02"></tt>, <tt><ref id=".PSC02"
3108 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
3111 <sect1><tt>.P816</tt><label id=".P816"><p>
3113 Enable the 65816 instruction set. This is a superset of the 65SC02 and
3114 6502 instruction sets.
3116 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3117 name=".PSC02"></tt> and <tt><ref id=".PC02" name=".PC02"></tt>
3120 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
3122 Set the page length for the listing. Must be followed by an integer
3123 constant. The value may be "unlimited", or in the range 32 to 127. The
3124 statement has no effect if no listing is generated. The default value is -1
3125 (unlimited) but may be overridden by the <tt/--pagelength/ command line
3126 option. Beware: Since ca65 is a one pass assembler, the listing is generated
3127 after assembly is complete, you cannot use multiple line lengths with one
3128 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
3133 .pagelength 66 ; Use 66 lines per listing page
3135 .pagelength unlimited ; Unlimited page length
3139 <sect1><tt>.PC02</tt><label id=".PC02"><p>
3141 Enable the 65C02 instructions set. This instruction set includes all
3142 6502 and 65SC02 instructions.
3144 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3145 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
3148 <sect1><tt>.POPCPU</tt><label id=".POPCPU"><p>
3150 Pop the last CPU setting from the stack, and activate it.
3152 This command will switch back to the CPU that was last pushed onto the CPU
3153 stack using the <tt><ref id=".PUSHCPU" name=".PUSHCPU"></tt> command, and
3154 remove this entry from the stack.
3156 The assembler will print an error message if the CPU stack is empty when
3157 this command is issued.
3159 See: <tt><ref id=".CPU" name=".CPU"></tt>, <tt><ref id=".PUSHCPU"
3160 name=".PUSHCPU"></tt>, <tt><ref id=".SETCPU" name=".SETCPU"></tt>
3163 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
3165 Pop the last pushed segment from the stack, and set it.
3167 This command will switch back to the segment that was last pushed onto the
3168 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
3169 command, and remove this entry from the stack.
3171 The assembler will print an error message if the segment stack is empty
3172 when this command is issued.
3174 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
3177 <sect1><tt>.PROC</tt><label id=".PROC"><p>
3179 Start a nested lexical level with the given name and adds a symbol with this
3180 name to the enclosing scope. All new symbols from now on are in the local
3181 lexical level and are accessible from outside only via <ref id="scopesyntax"
3182 name="explicit scope specification">. Symbols defined outside this local
3183 level may be accessed as long as their names are not used for new symbols
3184 inside the level. Symbols names in other lexical levels do not clash, so you
3185 may use the same names for identifiers. The lexical level ends when the
3186 <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read. Lexical levels
3187 may be nested up to a depth of 16 (this is an artificial limit to protect
3188 against errors in the source).
3190 Note: Macro names are always in the global level and in a separate name
3191 space. There is no special reason for this, it's just that I've never
3192 had any need for local macro definitions.
3197 .proc Clear ; Define Clear subroutine, start new level
3199 L1: sta Mem,y ; L1 is local and does not cause a
3200 ; duplicate symbol error if used in other
3203 bne L1 ; Reference local symbol
3205 .endproc ; Leave lexical level
3208 See: <tt/<ref id=".ENDPROC" name=".ENDPROC">/ and <tt/<ref id=".SCOPE"
3212 <sect1><tt>.PSC02</tt><label id=".PSC02"><p>
3214 Enable the 65SC02 instructions set. This instruction set includes all
3217 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PC02"
3218 name=".PC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
3221 <sect1><tt>.PUSHCPU</tt><label id=".PUSHCPU"><p>
3223 Push the currently active CPU onto a stack. The stack has a size of 8
3226 <tt/.PUSHCPU/ allows together with <tt><ref id=".POPCPU"
3227 name=".POPCPU"></tt> to switch to another CPU and to restore the old CPU
3228 later, without knowledge of the current CPU setting.
3230 The assembler will print an error message if the CPU stack is already full,
3231 when this command is issued.
3233 See: <tt><ref id=".CPU" name=".CPU"></tt>, <tt><ref id=".POPCPU"
3234 name=".POPCPU"></tt>, <tt><ref id=".SETCPU" name=".SETCPU"></tt>
3237 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
3239 Push the currently active segment onto a stack. The entries on the stack
3240 include the name of the segment and the segment type. The stack has a size
3243 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
3244 to switch to another segment and to restore the old segment later, without
3245 even knowing the name and type of the current segment.
3247 The assembler will print an error message if the segment stack is already
3248 full, when this command is issued.
3250 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
3253 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
3255 Switch back to relocatable mode. See the <tt><ref id=".ORG"
3256 name=".ORG"></tt> command.
3259 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
3261 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
3262 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
3263 a constant expression that tells how many times the commands in the body
3264 should get repeated. Optionally, a comma and an identifier may be specified.
3265 If this identifier is found in the body of the repeat statement, it is
3266 replaced by the current repeat count (starting with zero for the first time
3267 the body is repeated).
3269 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
3270 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
3271 level will be used, not the one from the outer level.
3275 The following macro will emit a string that is "encrypted" in that all
3276 characters of the string are XORed by the value $55.
3280 .repeat .strlen(Arg), I
3281 .byte .strat(Arg, I) ^ $55
3286 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
3289 <sect1><tt>.RES</tt><label id=".RES"><p>
3291 Reserve storage. The command is followed by one or two constant
3292 expressions. The first one is mandatory and defines, how many bytes of
3293 storage should be defined. The second, optional expression must by a
3294 constant byte value that will be used as value of the data. If there
3295 is no fill value given, the linker will use the value defined in the
3296 linker configuration file (default: zero).
3301 ; Reserve 12 bytes of memory with value $AA
3306 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
3308 Switch to the RODATA segment. The name of the RODATA segment is always
3309 "RODATA", so this is a shortcut for
3315 The RODATA segment is a segment that is used by the compiler for
3316 readonly data like string constants.
3318 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
3321 <sect1><tt>.SCOPE</tt><label id=".SCOPE"><p>
3323 Start a nested lexical level with the given name. All new symbols from now
3324 on are in the local lexical level and are accessible from outside only via
3325 <ref id="scopesyntax" name="explicit scope specification">. Symbols defined
3326 outside this local level may be accessed as long as their names are not used
3327 for new symbols inside the level. Symbols names in other lexical levels do
3328 not clash, so you may use the same names for identifiers. The lexical level
3329 ends when the <tt><ref id=".ENDSCOPE" name=".ENDSCOPE"></tt> command is
3330 read. Lexical levels may be nested up to a depth of 16 (this is an
3331 artificial limit to protect against errors in the source).
3333 Note: Macro names are always in the global level and in a separate name
3334 space. There is no special reason for this, it's just that I've never
3335 had any need for local macro definitions.
3340 .scope Error ; Start new scope named Error
3342 File = 1 ; File error
3343 Parse = 2 ; Parse error
3344 .endscope ; Close lexical level
3347 lda #Error::File ; Use symbol from scope Error
3350 See: <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/ and <tt/<ref id=".PROC"
3354 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
3356 Switch to another segment. Code and data is always emitted into a
3357 segment, that is, a named section of data. The default segment is
3358 "CODE". There may be up to 254 different segments per object file
3359 (and up to 65534 per executable). There are shortcut commands for
3360 the most common segments ("CODE", "DATA" and "BSS").
3362 The command is followed by a string containing the segment name (there are
3363 some constraints for the name - as a rule of thumb use only those segment
3364 names that would also be valid identifiers). There may also be an optional
3365 address size separated by a colon. See the section covering <tt/<ref
3366 id="address-sizes" name="address sizes">/ for more information.
3368 The default address size for a segment depends on the memory model specified
3369 on the command line. The default is "absolute", which means that you don't
3370 have to use an address size modifier in most cases.
3372 "absolute" means that the is a segment with 16 bit (absolute) addressing.
3373 That is, the segment will reside somewhere in core memory outside the zero
3374 page. "zeropage" (8 bit) means that the segment will be placed in the zero
3375 page and direct (short) addressing is possible for data in this segment.
3377 Beware: Only labels in a segment with the zeropage attribute are marked
3378 as reachable by short addressing. The `*' (PC counter) operator will
3379 work as in other segments and will create absolute variable values.
3381 Please note that a segment cannot have two different address sizes. A
3382 segment specified as zeropage cannot be declared as being absolute later.
3387 .segment "ROM2" ; Switch to ROM2 segment
3388 .segment "ZP2": zeropage ; New direct segment
3389 .segment "ZP2" ; Ok, will use last attribute
3390 .segment "ZP2": absolute ; Error, redecl mismatch
3393 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
3394 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref
3395 id=".RODATA" name=".RODATA"></tt>
3398 <sect1><tt>.SETCPU</tt><label id=".SETCPU"><p>
3400 Switch the CPU instruction set. The command is followed by a string that
3401 specifies the CPU. Possible values are those that can also be supplied to
3402 the <tt><ref id="option--cpu" name="--cpu"></tt> command line option,
3403 namely: 6502, 6502X, 65SC02, 65C02, 65816, sunplus and HuC6280. Please
3404 note that support for the sunplus CPU is not available in the freeware
3405 version, because the instruction set of the sunplus CPU is "proprietary
3408 See: <tt><ref id=".CPU" name=".CPU"></tt>,
3409 <tt><ref id=".IFP02" name=".IFP02"></tt>,
3410 <tt><ref id=".IFP816" name=".IFP816"></tt>,
3411 <tt><ref id=".IFPC02" name=".IFPC02"></tt>,
3412 <tt><ref id=".IFPSC02" name=".IFPSC02"></tt>,
3413 <tt><ref id=".P02" name=".P02"></tt>,
3414 <tt><ref id=".P816" name=".P816"></tt>,
3415 <tt><ref id=".PC02" name=".PC02"></tt>,
3416 <tt><ref id=".PSC02" name=".PSC02"></tt>
3419 <sect1><tt>.SMART</tt><label id=".SMART"><p>
3421 Switch on or off smart mode. The command must be followed by a '+' or '-'
3422 character to switch the option on or off respectively. The default is off
3423 (that is, the assembler doesn't try to be smart), but this default may be
3424 changed by the -s switch on the command line.
3426 In smart mode the assembler will do the following:
3429 <item>Track usage of the <tt/REP/ and <tt/SEP/ instructions in 65816 mode
3430 and update the operand sizes accordingly. If the operand of such an
3431 instruction cannot be evaluated by the assembler (for example, because
3432 the operand is an imported symbol), a warning is issued. Beware: Since
3433 the assembler cannot trace the execution flow this may lead to false
3434 results in some cases. If in doubt, use the <tt/.Inn/ and <tt/.Ann/
3435 instructions to tell the assembler about the current settings.
3436 <item>In 65816 mode, replace a <tt/RTS/ instruction by <tt/RTL/ if it is
3437 used within a procedure declared as <tt/far/, or if the procedure has
3438 no explicit address specification, but it is <tt/far/ because of the
3446 .smart - ; Stop being smart
3449 See: <tt><ref id=".A16" name=".A16"></tt>,
3450 <tt><ref id=".A8" name=".A8"></tt>,
3451 <tt><ref id=".I16" name=".I16"></tt>,
3452 <tt><ref id=".I8" name=".I8"></tt>
3455 <sect1><tt>.STRUCT</tt><label id=".STRUCT"><p>
3457 Starts a struct definition. Structs are covered in a separate section named
3458 <ref id="structs" name=""Structs and unions"">.
3460 See: <tt><ref id=".ENDSTRUCT" name=".ENDSTRUCT"></tt>
3463 <sect1><tt>.SUNPLUS</tt><label id=".SUNPLUS"><p>
3465 Enable the SunPlus instructions set. This command will not work in the
3466 freeware version of the assembler, because the instruction set is
3467 "proprietary and confidential".
3469 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3470 name=".PSC02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt>, and
3471 <tt><ref id=".P816" name=".P816"></tt>
3474 <sect1><tt>.TAG</tt><label id=".TAG"><p>
3476 Allocate space for a struct or union.
3487 .tag Point ; Allocate 4 bytes
3491 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
3493 Force an assembly warning. The assembler will output a warning message
3494 preceded by "User warning". This warning will always be output, even if
3495 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
3496 command line option.
3498 This command may be used to output possible problems when assembling
3507 .warning "Forward jump in jne, cannot optimize!"
3517 See also the <tt><ref id=".ERROR" name=".ERROR"></tt> and <tt><ref id=".OUT"
3518 name=".OUT"></tt> directives.
3521 <sect1><tt>.WORD</tt><label id=".WORD"><p>
3523 Define word sized data. Must be followed by a sequence of (word ranged,
3524 but not necessarily constant) expressions.
3529 .word $0D00, $AF13, _Clear
3533 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
3535 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
3536 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
3540 .segment "ZEROPAGE", zeropage
3543 Because of the "zeropage" attribute, labels declared in this segment are
3544 addressed using direct addressing mode if possible. You <em/must/ instruct
3545 the linker to place this segment somewhere in the address range 0..$FF
3546 otherwise you will get errors.
3548 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
3552 <sect>Macros<label id="macros"><p>
3555 <sect1>Introduction<p>
3557 Macros may be thought of as "parametrized super instructions". Macros are
3558 sequences of tokens that have a name. If that name is used in the source
3559 file, the macro is "expanded", that is, it is replaced by the tokens that
3560 were specified when the macro was defined.
3563 <sect1>Macros without parameters<p>
3565 In it's simplest form, a macro does not have parameters. Here's an
3569 .macro asr ; Arithmetic shift right
3570 cmp #$80 ; Put bit 7 into carry
3571 ror ; Rotate right with carry
3575 The macro above consists of two real instructions, that are inserted into
3576 the code, whenever the macro is expanded. Macro expansion is simply done
3577 by using the name, like this:
3586 <sect1>Parametrized macros<p>
3588 When using macro parameters, macros can be even more useful:
3602 When calling the macro, you may give a parameter, and each occurrence of
3603 the name "addr" in the macro definition will be replaced by the given
3622 A macro may have more than one parameter, in this case, the parameters
3623 are separated by commas. You are free to give less parameters than the
3624 macro actually takes in the definition. You may also leave intermediate
3625 parameters empty. Empty parameters are replaced by empty space (that is,
3626 they are removed when the macro is expanded). If you have a look at our
3627 macro definition above, you will see, that replacing the "addr" parameter
3628 by nothing will lead to wrong code in most lines. To help you, writing
3629 macros with a variable parameter list, there are some control commands:
3631 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
3632 returns true, if there are any tokens on the remainder of the line. Since
3633 empty parameters are replaced by nothing, this may be used to test if a given
3634 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
3637 Look at this example:
3640 .macro ldaxy a, x, y
3653 This macro may be called as follows:
3656 ldaxy 1, 2, 3 ; Load all three registers
3658 ldaxy 1, , 3 ; Load only a and y
3660 ldaxy , , 3 ; Load y only
3663 There's another helper command for determining, which macro parameters are
3664 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is
3665 replaced by the parameter count given, <em/including/ intermediate empty macro
3669 ldaxy 1 ; .PARAMCOUNT = 1
3670 ldaxy 1,,3 ; .PARAMCOUNT = 3
3671 ldaxy 1,2 ; .PARAMCOUNT = 2
3672 ldaxy 1, ; .PARAMCOUNT = 2
3673 ldaxy 1,2,3 ; .PARAMCOUNT = 3
3676 Macro parameters may optionally be enclosed into curly braces. This allows the
3677 inclusion of tokens that would otherwise terminate the parameter (the comma in
3678 case of a macro parameter).
3681 .macro foo arg1, arg2
3685 foo ($00,x) ; Two parameters passed
3686 foo {($00,x)} ; One parameter passed
3689 In the first case, the macro is called with two parameters: '<tt/($00/'
3690 and 'x)'. The comma is not passed to the macro, since it is part of the
3691 calling sequence, not the parameters.
3693 In the second case, '($00,x)' is passed to the macro, this time
3694 including the comma.
3697 <sect1>Detecting parameter types<p>
3699 Sometimes it is nice to write a macro that acts differently depending on the
3700 type of the argument supplied. An example would be a macro that loads a 16 bit
3701 value from either an immediate operand, or from memory. The <tt/<ref
3702 id=".MATCH" name=".MATCH">/ and <tt/<ref id=".XMATCH" name=".XMATCH">/
3703 functions will allow you to do exactly this:
3707 .if (.match (.left (1, {arg}), #))
3709 lda #<(.right (.tcount ({arg})-1, {arg}))
3710 ldx #>(.right (.tcount ({arg})-1, {arg}))
3712 ; assume absolute or zero page
3719 Using the <tt/<ref id=".MATCH" name=".MATCH">/ function, the macro is able to
3720 check if its argument begins with a hash mark. If so, two immediate loads are
3721 emitted, Otherwise a load from an absolute zero page memory location is
3722 assumed. Please note how the curly braces are used to enclose parameters to
3723 pseudo functions handling token lists. This is necessary, because the token
3724 lists may include commas or parens, which would be treated by the assembler
3727 The macro can be used as
3732 ldax #$1234 ; X=$12, A=$34
3734 ldax foo ; X=$56, A=$78
3738 <sect1>Recursive macros<p>
3740 Macros may be used recursively:
3743 .macro push r1, r2, r3
3752 There's also a special macro to help writing recursive macros: <tt><ref
3753 id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion
3757 .macro push r1, r2, r3, r4, r5, r6, r7
3759 ; First parameter is empty
3765 push r2, r3, r4, r5, r6, r7
3769 When expanding this macro, the expansion will push all given parameters
3770 until an empty one is encountered. The macro may be called like this:
3773 push $20, $21, $32 ; Push 3 ZP locations
3774 push $21 ; Push one ZP location
3778 <sect1>Local symbols inside macros<p>
3780 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
3781 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
3782 Have a look at the inc16 macro above. Here is it again:
3796 If you have a closer look at the code, you will notice, that it could be
3797 written more efficiently, like this:
3808 But imagine what happens, if you use this macro twice? Since the label
3809 "Skip" has the same name both times, you get a "duplicate symbol" error.
3810 Without a way to circumvent this problem, macros are not as useful, as
3811 they could be. One solution is, to start a new lexical block inside the
3825 Now the label is local to the block and not visible outside. However,
3826 sometimes you want a label inside the macro to be visible outside. To make
3827 that possible, there's a new command that's only usable inside a macro
3828 definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one
3829 or more symbols as local to the macro expansion. The names of local variables
3830 are replaced by a unique name in each separate macro expansion. So we could
3831 also solve the problem above by using <tt/.LOCAL/:
3835 .local Skip ; Make Skip a local symbol
3842 Skip: ; Not visible outside
3847 <sect1>C style macros<p>
3849 Starting with version 2.5 of the assembler, there is a second macro type
3850 available: C style macros using the <tt/.DEFINE/ directive. These macros are
3851 similar to the classic macro type described above, but behaviour is sometimes
3856 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
3857 span more than a line. You may use line continuation (see <tt><ref
3858 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
3859 more than one line for increased readability, but the macro itself
3860 may not contain an end-of-line token.
3862 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
3863 the name space with classic macros, but they are detected and replaced
3864 at the scanner level. While classic macros may be used in every place,
3865 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
3866 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
3867 they are more versatile in some situations.
3869 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
3870 parameters. While classic macros may have empty parameters, this is
3871 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
3872 For this macro type, the number of actual parameters must match
3873 exactly the number of formal parameters.
3875 To make this possible, formal parameters are enclosed in braces when
3876 defining the macro. If there are no parameters, the empty braces may
3879 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
3880 contain end-of-line tokens, there are things that cannot be done. They
3881 may not contain several processor instructions for example. So, while
3882 some things may be done with both macro types, each type has special
3883 usages. The types complement each other.
3887 Let's look at a few examples to make the advantages and disadvantages
3890 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
3891 following <tt/.DEFINE/:
3896 foo EQU $1234 ; This is accepted now
3899 You may use the directive to define string constants used elsewhere:
3902 ; Define the version number
3903 .define VERSION "12.3a"
3909 Macros with parameters may also be useful:
3912 .define DEBUG(message) .out message
3914 DEBUG "Assembling include file #3"
3917 Note that, while formal parameters have to be placed in braces, this is
3918 not true for the actual parameters. Beware: Since the assembler cannot
3919 detect the end of one parameter, only the first token is used. If you
3920 don't like that, use classic macros instead:
3928 (This is an example where a problem can be solved with both macro types).
3931 <sect1>Characters in macros<p>
3933 When using the <ref id="option-t" name="-t"> option, characters are translated
3934 into the target character set of the specific machine. However, this happens
3935 as late as possible. This means that strings are translated if they are part
3936 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
3937 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
3938 used as part of an expression.
3940 This behaviour is very intuitive outside of macros but may be confusing when
3941 doing more complex macros. If you compare characters against numeric values,
3942 be sure to take the translation into account.
3947 <sect>Macro packages<label id="macropackages"><p>
3949 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
3950 macro packages may be included with just one command. Available macro packages
3954 <sect1><tt>.MACPACK generic</tt><p>
3956 This macro package defines macros that are useful in almost any program.
3957 Currently, two macros are defined:
3972 <sect1><tt>.MACPACK longbranch</tt><p>
3974 This macro package defines long conditional jumps. They are named like the
3975 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
3976 definition for the "<tt/jeq/" macro, the other macros are built using the same
3981 .if .def(Target) .and ((*+2)-(Target) <= 127)
3990 All macros expand to a short branch, if the label is already defined (back
3991 jump) and is reachable with a short jump. Otherwise the macro expands to a
3992 conditional branch with the branch condition inverted, followed by an absolute
3993 jump to the actual branch target.
3995 The package defines the following macros:
3998 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
4003 <sect1><tt>.MACPACK cbm</tt><p>
4005 The cbm macro package will define a macro named <tt/scrcode/. It takes a
4006 string as argument and places this string into memory translated into screen
4010 <sect1><tt>.MACPACK cpu</tt><p>
4012 This macro package does not define any macros but constants used to examine
4013 the value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable. For
4014 each supported CPU a constant similar to
4026 is defined. These constants may be used to determine the exact type of the
4027 currently enabled CPU. In addition to that, for each CPU instruction set,
4028 another constant is defined:
4040 The value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable may
4041 be checked with <tt/<ref id="operators" name=".BITAND">/ to determine if the
4042 currently enabled CPU supports a specific instruction set. For example the
4043 65C02 supports all instructions of the 65SC02 CPU, so it has the
4044 <tt/CPU_ISET_65SC02/ bit set in addition to its native <tt/CPU_ISET_65C02/
4048 .if (.cpu .bitand CPU_ISET_65SC02)
4056 it is possible to determine if the
4062 instruction is supported, which is the case for the 65SC02, 65C02 and 65816
4063 CPUs (the latter two are upwards compatible to the 65SC02).
4067 <sect>Predefined constants<label id="predefined-constants"><p>
4069 For better orthogonality, the assembler defines similar symbols as the
4070 compiler, depending on the target system selected:
4073 <item><tt/__APPLE2__/ - Target system is <tt/apple2/
4074 <item><tt/__APPLE2ENH__/ - Target system is <tt/apple2enh/
4075 <item><tt/__ATARI__/ - Target system is <tt/atari/
4076 <item><tt/__ATMOS__/ - Target system is <tt/atmos/
4077 <item><tt/__BBC__/ - Target system is <tt/bbc/
4078 <item><tt/__C128__/ - Target system is <tt/c128/
4079 <item><tt/__C16__/ - Target system is <tt/c16/
4080 <item><tt/__C64__/ - Target system is <tt/c64/
4081 <item><tt/__CBM__/ - Target is a Commodore system
4082 <item><tt/__CBM510__/ - Target system is <tt/cbm510/
4083 <item><tt/__CBM610__/ - Target system is <tt/cbm610/
4084 <item><tt/__GEOS__/ - Target system is <tt/geos/
4085 <item><tt/__LUNIX__/ - Target system is <tt/lunix/
4086 <item><tt/__NES__/ - Target system is <tt/nes/
4087 <item><tt/__PET__/ - Target system is <tt/pet/
4088 <item><tt/__PLUS4__/ - Target system is <tt/plus4/
4089 <item><tt/__SUPERVISION__/ - Target system is <tt/supervision/
4090 <item><tt/__VIC20__/ - Target system is <tt/vic20/
4094 <sect>Structs and unions<label id="structs"><p>
4096 <sect1>Structs and unions Overview<p>
4098 Structs and unions are special forms of <ref id="scopes" name="scopes">. They
4099 are to some degree comparable to their C counterparts. Both have a list of
4100 members. Each member allocates storage and may optionally have a name, which,
4101 in case of a struct, is the offset from the beginning and, in case of a union,
4105 <sect1>Declaration<p>
4107 Here is an example for a very simple struct with two members and a total size
4117 A union shares the total space between all its members, its size is the same
4118 as that of the largest member.
4120 A struct or union must not necessarily have a name. If it is anonymous, no
4121 local scope is opened, the identifiers used to name the members are placed
4122 into the current scope instead.
4124 A struct may contain unnamed members and definitions of local structs. The
4125 storage allocators may contain a multiplier, as in the example below:
4130 .word 2 ; Allocate two words
4137 <sect1>The <tt/.TAG/ keyword<p>
4139 Using the <ref id=".TAG" name=".TAG"> keyword, it is possible to reserve space
4140 for an already defined struct or unions within another struct:
4154 Space for a struct or union may be allocated using the <ref id=".TAG"
4155 name=".TAG"> directive.
4161 Currently, members are just offsets from the start of the struct or union. To
4162 access a field of a struct, the member offset has to be added to the address
4163 of the struct itself:
4166 lda C+Circle::Radius ; Load circle radius into A
4169 This may change in a future version of the assembler.
4172 <sect1>Limitations<p>
4174 Structs and unions are currently implemented as nested symbol tables (in fact,
4175 they were a by-product of the improved scoping rules). Currently, the
4176 assembler has no idea of types. This means that the <ref id=".TAG"
4177 name=".TAG"> keyword will only allocate space. You won't be able to initialize
4178 variables declared with <ref id=".TAG" name=".TAG">, and adding an embedded
4179 structure to another structure with <ref id=".TAG" name=".TAG"> will not make
4180 this structure accessible by using the '::' operator.
4184 <sect>Module constructors/destructors<label id="condes"><p>
4186 <em>Note:</em> This section applies mostly to C programs, so the explanation
4187 below uses examples from the C libraries. However, the feature may also be
4188 useful for assembler programs.
4191 <sect1>Module constructors/destructors Overview<p>
4193 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
4194 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
4195 name=".INTERRUPTOR"></tt> keywords it it possible to export functions in a
4196 special way. The linker is able to generate tables with all functions of a
4197 specific type. Such a table will <em>only</em> include symbols from object
4198 files that are linked into a specific executable. This may be used to add
4199 initialization and cleanup code for library modules, or a table of interrupt
4202 The C heap functions are an example where module initialization code is used.
4203 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
4204 variables that contain the start and the end of the heap, pointers to the free
4205 list and so on. Since the end of the heap depends on the size and start of the
4206 stack, it must be initialized at runtime. However, initializing these
4207 variables for programs that do not use the heap are a waste of time and
4210 So the central module defines a function that contains initialization code and
4211 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
4212 this module is added to an executable by the linker, the initialization
4213 function will be placed into the table of constructors by the linker. The C
4214 startup code will call all constructors before <tt/main/ and all destructors
4215 after <tt/main/, so without any further work, the heap initialization code is
4216 called once the module is linked in.
4218 While it would be possible to add explicit calls to initialization functions
4219 in the startup code, the new approach has several advantages:
4223 If a module is not included, the initialization code is not linked in and not
4224 called. So you don't pay for things you don't need.
4227 Adding another library that needs initialization does not mean that the
4228 startup code has to be changed. Before we had module constructors and
4229 destructors, the startup code for all systems had to be adjusted to call the
4230 new initialization code.
4233 The feature saves memory: Each additional initialization function needs just
4234 two bytes in the table (a pointer to the function).
4239 <sect1>Calling order<p>
4241 The symbols are sorted in increasing priority order by the linker when using
4242 one of the builtin linker configurations, so the functions with lower
4243 priorities come first and are followed by those with higher priorities. The C
4244 library runtime subroutine that walks over the function tables calls the
4245 functions starting from the top of the table - which means that functions with
4246 a high priority are called first.
4248 So when using the C runtime, functions are called with high priority functions
4249 first, followed by low priority functions.
4254 When using these special symbols, please take care of the following:
4259 The linker will only generate function tables, it will not generate code to
4260 call these functions. If you're using the feature in some other than the
4261 existing C environments, you have to write code to call all functions in a
4262 linker generated table yourself. See the <tt/condes/ and <tt/callirq/ modules
4263 in the C runtime for an example on how to do this.
4266 The linker will only add addresses of functions that are in modules linked to
4267 the executable. This means that you have to be careful where to place the
4268 condes functions. If initialization or an irq handler is needed for a group of
4269 functions, be sure to place the function into a module that is linked in
4270 regardless of which function is called by the user.
4273 The linker will generate the tables only when requested to do so by the
4274 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
4275 be requested separately.
4278 Constructors and destructors may have priorities. These priorities determine
4279 the order of the functions in the table. If your initialization or cleanup code
4280 does depend on other initialization or cleanup code, you have to choose the
4281 priority for the functions accordingly.
4284 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
4285 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
4286 name=".INTERRUPTOR"></tt> statements, there is also a more generic command:
4287 <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to specify an
4288 additional type. Predefined types are 0 (constructor), 1 (destructor) and 2
4289 (interruptor). The linker generates a separate table for each type on request.
4294 <sect>Porting sources from other assemblers<p>
4296 Sometimes it is necessary to port code written for older assemblers to ca65.
4297 In some cases, this can be done without any changes to the source code by
4298 using the emulation features of ca65 (see <tt><ref id=".FEATURE"
4299 name=".FEATURE"></tt>). In other cases, it is necessary to make changes to the
4302 Probably the biggest difference is the handling of the <tt><ref id=".ORG"
4303 name=".ORG"></tt> directive. ca65 generates relocatable code, and placement is
4304 done by the linker. Most other assemblers generate absolute code, placement is
4305 done within the assembler and there is no external linker.
4307 In general it is not a good idea to write new code using the emulation
4308 features of the assembler, but there may be situations where even this rule is
4313 You need to use some of the ca65 emulation features to simulate the behaviour
4314 of such simple assemblers.
4317 <item>Prepare your sourcecode like this:
4320 ; if you want TASS style labels without colons
4321 .feature labels_without_colons
4323 ; if you want TASS style character constants
4324 ; ("a" instead of the default 'a')
4325 .feature loose_char_term
4327 .word *+2 ; the cbm load address
4332 notice that the two emulation features are mostly useful for porting
4333 sources originally written in/for TASS, they are not needed for the
4334 actual "simple assembler operation" and are not recommended if you are
4335 writing new code from scratch.
4337 <item>Replace all program counter assignments (which are not possible in ca65
4338 by default, and the respective emulation feature works different from what
4339 you'd expect) by another way to skip to memory locations, for example the
4340 <tt><ref id=".RES" name=".RES"></tt> directive.
4344 .res $2000-* ; reserve memory up to $2000
4347 Please note that other than the original TASS, ca65 can never move the program
4348 counter backwards - think of it as if you are assembling to disk with TASS.
4350 <item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.goto/ etc.) must be
4351 rewritten to match ca65 syntax. Most importantly notice that due to the lack
4352 of <tt/.goto/, everything involving loops must be replaced by
4353 <tt><ref id=".REPEAT" name=".REPEAT"></tt>.
4355 <item>To assemble code to a different address than it is executed at, use the
4356 <tt><ref id=".ORG" name=".ORG"></tt> directive instead of
4357 <tt/.offs/-constructs.
4364 .reloc ; back to normal
4367 <item>Then assemble like this:
4370 cl65 --start-addr 0x0ffe -t none myprog.s -o myprog.prg
4373 Note that you need to use the actual start address minus two, since two bytes
4374 are used for the cbm load address.
4379 <sect>Bugs/Feedback<p>
4381 If you have problems using the assembler, if you find any bugs, or if
4382 you're doing something interesting with the assembler, I would be glad to
4383 hear from you. Feel free to contact me by email
4384 (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
4390 ca65 (and all cc65 binutils) are (C) Copyright 1998-2003 Ullrich von
4391 Bassewitz. For usage of the binaries and/or sources the following
4392 conditions do apply:
4394 This software is provided 'as-is', without any expressed or implied
4395 warranty. In no event will the authors be held liable for any damages
4396 arising from the use of this software.
4398 Permission is granted to anyone to use this software for any purpose,
4399 including commercial applications, and to alter it and redistribute it
4400 freely, subject to the following restrictions:
4403 <item> The origin of this software must not be misrepresented; you must not
4404 claim that you wrote the original software. If you use this software
4405 in a product, an acknowledgment in the product documentation would be
4406 appreciated but is not required.
4407 <item> Altered source versions must be plainly marked as such, and must not
4408 be misrepresented as being the original software.
4409 <item> This notice may not be removed or altered from any source