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 --debug-info Add debug info to object file
110 --feature name Set an emulation feature
111 --forget-inc-paths Forget include search paths
112 --help Help (this text)
113 --ignore-case Ignore case of symbols
114 --include-dir dir Set an include directory search path
115 --listing Create a listing if assembly was ok
116 --list-bytes n Maximum number of bytes per listing line
117 --macpack-dir dir Set a macro package directory
118 --memory-model model Set the memory model
119 --pagelength n Set the page length for the listing
120 --smart Enable smart mode
121 --target sys Set the target system
122 --verbose Increase verbosity
123 --version Print the assembler version
124 ---------------------------------------------------------------------------
128 <sect1>Command line options in detail<p>
130 Here is a description of all the command line options:
134 <label id="option--bin-include-dir">
135 <tag><tt>--bin-include-dir dir</tt></tag>
137 Name a directory which is searched for binary include files. The option
138 may be used more than once to specify more than one directory to search. The
139 current directory is always searched first before considering any
140 additional directories. See also the section about <ref id="search-paths"
141 name="search paths">.
144 <label id="option--cpu">
145 <tag><tt>--cpu type</tt></tag>
147 Set the default for the CPU type. The option takes a parameter, which
150 6502, 65SC02, 65C02, 65816, sunplus, sweet16, HuC6280
152 The sunplus cpu is not available in the freeware version, because the
153 instruction set is "proprietary and confidential".
156 <label id="option--feature">
157 <tag><tt>--feature name</tt></tag>
159 Enable an emulation feature. This is identical as using <tt/.FEATURE/
160 in the source with two exceptions: Feature names must be lower case, and
161 each feature must be specified by using an extra <tt/--feature/ option,
162 comma separated lists are not allowed.
164 See the discussion of the <tt><ref id=".FEATURE" name=".FEATURE"></tt>
165 command for a list of emulation features.
168 <label id="option--forget-inc-paths">
169 <tag><tt>--forget-inc-paths</tt></tag>
171 Forget the builtin include paths. This is most useful when building
172 customized assembler modules, in which case the standard header files should
176 <label id="option-g">
177 <tag><tt>-g, --debug-info</tt></tag>
179 When this option (or the equivalent control command <tt/.DEBUGINFO/) is
180 used, the assembler will add a section to the object file that contains
181 all symbols (including local ones) together with the symbol values and
182 source file positions. The linker will put these additional symbols into
183 the VICE label file, so even local symbols can be seen in the VICE
187 <label id="option-h">
188 <tag><tt>-h, --help</tt></tag>
190 Print the short option summary shown above.
193 <label id="option-i">
194 <tag><tt>-i, --ignore-case</tt></tag>
196 This option makes the assembler case insensitive on identifiers and labels.
197 This option will override the default, but may itself be overridden by the
198 <tt><ref id=".CASE" name=".CASE"></tt> control command.
201 <label id="option-l">
202 <tag><tt>-l, --listing</tt></tag>
204 Generate an assembler listing. The listing file will always have the
205 name of the main input file with the extension replaced by ".lst". This
206 may change in future versions.
209 <label id="option--list-bytes">
210 <tag><tt>--list-bytes n</tt></tag>
212 Set the maximum number of bytes printed in the listing for one line of
213 input. See the <tt><ref id=".LISTBYTES" name=".LISTBYTES"></tt> directive
214 for more information. The value zero can be used to encode an unlimited
215 number of printed bytes.
218 <label id="option--macpack-dir">
219 <tag><tt>--macpack-dir dir</tt></tag>
221 This options allows to specify a directory containing macro files that are
222 used instead of the builtin images when a <tt><ref id=".MACPACK"
223 name=".MACPACK"></tt> directive is encountered. If <tt>--macpack-dir</tt>
224 was specified, a <tt>.mac</tt> extension is added to the package name and
225 the resulting file is loaded from the given directory. This is most useful
226 when debugging the builtin macro packages.
229 <label id="option-mm">
230 <tag><tt>-mm model, --memory-model model</tt></tag>
232 Define the default memory model. Possible model specifiers are near, far and
236 <label id="option-o">
237 <tag><tt>-o name</tt></tag>
239 The default output name is the name of the input file with the extension
240 replaced by ".o". If you don't like that, you may give another name with
241 the -o option. The output file will be placed in the same directory as
242 the source file, or, if -o is given, the full path in this name is used.
245 <label id="option--pagelength">
246 <tag><tt>--pagelength n</tt></tag>
248 sets the length of a listing page in lines. See the <tt><ref
249 id=".PAGELENGTH" name=".PAGELENGTH"></tt> directive for more information.
252 <label id="option-s">
253 <tag><tt>-s, --smart-mode</tt></tag>
255 In smart mode (enabled by -s or the <tt><ref id=".SMART" name=".SMART"></tt>
256 pseudo instruction) the assembler will track usage of the <tt/REP/ and
257 <tt/SEP/ instructions in 65816 mode and update the operand sizes
258 accordingly. If the operand of such an instruction cannot be evaluated by
259 the assembler (for example, because the operand is an imported symbol), a
262 Beware: Since the assembler cannot trace the execution flow this may
263 lead to false results in some cases. If in doubt, use the .ixx and .axx
264 instructions to tell the assembler about the current settings. Smart
265 mode is off by default.
268 <label id="option-t">
269 <tag><tt>-t sys, --target sys</tt></tag>
271 Set the target system. This will enable translation of character strings
272 and character constants into the character set of the target platform.
273 The default for the target system is "none", which means that no translation
274 will take place. The assembler supports the same target systems as the
275 compiler, see there for a list.
278 <label id="option-v">
279 <tag><tt>-v, --verbose</tt></tag>
281 Increase the assembler verbosity. Usually only needed for debugging
282 purposes. You may use this option more than one time for even more
286 <label id="option-D">
287 <tag><tt>-D</tt></tag>
289 This option allows you to define symbols on the command line. Without a
290 value, the symbol is defined with the value zero. When giving a value,
291 you may use the '$' prefix for hexadecimal symbols. Please note
292 that for some operating systems, '$' has a special meaning, so
293 you may have to quote the expression.
296 <label id="option-I">
297 <tag><tt>-I dir, --include-dir dir</tt></tag>
299 Name a directory which is searched for include files. The option may be
300 used more than once to specify more than one directory to search. The
301 current directory is always searched first before considering any
302 additional directories. See also the section about <ref id="search-paths"
303 name="search paths">.
306 <label id="option-U">
307 <tag><tt>-U, --auto-import</tt></tag>
309 Mark symbols that are not defined in the sources as imported symbols. This
310 should be used with care since it delays error messages about typos and such
311 until the linker is run. The compiler uses the equivalent of this switch
312 (<tt><ref id=".AUTOIMPORT" name=".AUTOIMPORT"></tt>) to enable auto imported
313 symbols for the runtime library. However, the compiler is supposed to
314 generate code that runs through the assembler without problems, something
315 which is not always true for assembler programmers.
318 <label id="option-V">
319 <tag><tt>-V, --version</tt></tag>
321 Print the version number of the assembler. If you send any suggestions
322 or bugfixes, please include the version number.
325 <label id="option-W">
326 <tag><tt>-Wn</tt></tag>
328 Set the warning level for the assembler. Using -W2 the assembler will
329 even warn about such things like unused imported symbols. The default
330 warning level is 1, and it would probably be silly to set it to
338 <sect>Search paths<label id="search-paths"><p>
340 Normal include files are searched in the following places:
343 <item>The current directory.
344 <item>A compiled-in directory, which is often <tt>/usr/lib/cc65/asminc</tt>
346 <item>The value of the environment variable <tt/CA65_INC/ if it is defined.
347 <item>A subdirectory named <tt/asminc/ of the directory defined in the
348 environment variable <tt/CC65_HOME/, if it is defined.
349 <item>Any directory added with the <tt/<ref id="option-I" name="-I">/ option
353 Binary include files are searched in the following places:
356 <item>The current directory.
357 <item>Any directory added with the <tt/<ref id="option--bin-include-dir"
358 name="--bin-include-dir">/ option on the command line.
363 <sect>Input format<p>
365 <sect1>Assembler syntax<p>
367 The assembler accepts the standard 6502/65816 assembler syntax. One line may
368 contain a label (which is identified by a colon), and, in addition to the
369 label, an assembler mnemonic, a macro, or a control command (see section <ref
370 id="control-commands" name="Control Commands"> for supported control
371 commands). Alternatively, the line may contain a symbol definition using
372 the '=' token. Everything after a semicolon is handled as a comment (that is,
375 Here are some examples for valid input lines:
378 Label: ; A label and a comment
379 lda #$20 ; A 6502 instruction plus comment
380 L1: ldx #$20 ; Same with label
381 L2: .byte "Hello world" ; Label plus control command
382 mymac $20 ; Macro expansion
383 MySym = 3*L1 ; Symbol definition
384 MaSym = Label ; Another symbol
387 The assembler accepts
390 <item>all valid 6502 mnemonics when in 6502 mode (the default or after the
391 <tt><ref id=".P02" name=".P02"></tt> command was given).
392 <item>all valid 6502 mnemonics plus a set of illegal instructions when in
393 <ref id="6502X-mode" name="6502X mode">.
394 <item>all valid 65SC02 mnemonics when in 65SC02 mode (after the
395 <tt><ref id=".PSC02" name=".PSC02"></tt> command was given).
396 <item>all valid 65C02 mnemonics when in 65C02 mode (after the
397 <tt><ref id=".PC02" name=".PC02"></tt> command was given).
398 <item>all valid 65618 mnemonics when in 65816 mode (after the
399 <tt><ref id=".P816" name=".P816"></tt> command was given).
400 <item>all valid SunPlus mnemonics when in SunPlus mode (after the
401 <tt><ref id=".SUNPLUS" name=".SUNPLUS"></tt> command was given).
407 In 65816 mode several aliases are accepted in addition to the official
411 BGE is an alias for BCS
412 BLT is an alias for BCC
413 CPA is an alias for CMP
414 DEA is an alias for DEC A
415 INA is an alias for INC A
416 SWA is an alias for XBA
417 TAD is an alias for TCD
418 TAS is an alias for TCS
419 TDA is an alias for TDC
420 TSA is an alias for TSC
425 <sect1>6502X mode<label id="6502X-mode"><p>
427 6502X mode is an extension to the normal 6502 mode. In this mode, several
428 mnemonics for illegal instructions of the NMOS 6502 CPUs are accepted. Since
429 these instructions are illegal, there are no official mnemonics for them. The
430 unofficial ones are taken from <htmlurl
431 url="http://oxyron.net/graham/opcodes02.html"
432 name="http://oxyron.net/graham/opcodes02.html">. Please note that only the
433 ones marked as "stable" are supported. The following table uses information
434 from the mentioned web page, for more information, see there.
437 <item><tt>ALR: A:=(A and #{imm})*2;</tt>
438 <item><tt>ANC: A:=A and #{imm};</tt> Generates opcode $0B.
439 <item><tt>ARR: A:=(A and #{imm})/2;</tt>
440 <item><tt>AXS: X:=A and X-#{imm};</tt>
441 <item><tt>DCP: {adr}:={adr}-1; A-{adr};</tt>
442 <item><tt>ISC: {adr}:={adr}+1; A:=A-{adr};</tt>
443 <item><tt>LAS: A,X,S:={adr} and S;</tt>
444 <item><tt>LAX: A,X:={adr};</tt>
445 <item><tt>RLA: {adr}:={adr}rol; A:=A and {adr};</tt>
446 <item><tt>RRA: {adr}:={adr}ror; A:=A adc {adr};</tt>
447 <item><tt>SAX: {adr}:=A and X;</tt>
448 <item><tt>SLO: {adr}:={adr}*2; A:=A or {adr};</tt>
449 <item><tt>SRE: {adr}:={adr}/2; A:=A xor {adr};</tt>
454 <sect1>sweet16 mode<label id="sweet16-mode"><p>
456 SWEET 16 is an interpreter for a pseudo 16 bit CPU written by Steve Wozniak
457 for the Apple ][ machines. It is available in the Apple ][ ROM. ca65 can
458 generate code for this pseudo CPU when switched into sweet16 mode. The
459 following is special in sweet16 mode:
463 <item>The '@' character denotes indirect addressing and is no longer available
464 for cheap local labels. If you need cheap local labels, you will have to
465 switch to another lead character using the <tt/<ref id=".LOCALCHAR"
466 name=".LOCALCHAR">/ command.
468 <item>Registers are specified using <tt/R0/ .. <tt/R15/. In sweet16 mode,
469 these identifiers are reserved words.
473 Please note that the assembler does neither supply the interpreter needed for
474 SWEET 16 code, nor the zero page locations needed for the SWEET 16 registers,
475 nor does it call the interpreter. All this must be done by your program. Apple
476 ][ programmers do probably know how to use sweet16 mode.
478 For more information about SWEET 16, see
479 <htmlurl url="http://www.6502.org/source/interpreters/sweet16.htm"
480 name="http://www.6502.org/source/interpreters/sweet16.htm">.
483 <sect1>Number format<p>
485 For literal values, the assembler accepts the widely used number formats: A
486 preceding '$' or a trailing 'h' denotes a hex value, a preceding '%'
487 denotes a binary value, and a bare number is interpreted as a decimal. There
488 are currently no octal values and no floats.
491 <sect1>Conditional assembly<p>
493 Please note that when using the conditional directives (<tt/.IF/ and friends),
494 the input must consist of valid assembler tokens, even in <tt/.IF/ branches
495 that are not assembled. The reason for this behaviour is that the assembler
496 must still be able to detect the ending tokens (like <tt/.ENDIF/), so
497 conversion of the input stream into tokens still takes place. As a consequence
498 conditional assembly directives may <bf/not/ be used to prevent normal text
499 (used as a comment or similar) from being assembled. <p>
505 <sect1>Expression evaluation<p>
507 All expressions are evaluated with (at least) 32 bit precision. An
508 expression may contain constant values and any combination of internal and
509 external symbols. Expressions that cannot be evaluated at assembly time
510 are stored inside the object file for evaluation by the linker.
511 Expressions referencing imported symbols must always be evaluated by the
515 <sect1>Size of an expression result<p>
517 Sometimes, the assembler must know about the size of the value that is the
518 result of an expression. This is usually the case, if a decision has to be
519 made, to generate a zero page or an absolute memory references. In this
520 case, the assembler has to make some assumptions about the result of an
524 <item> If the result of an expression is constant, the actual value is
525 checked to see if it's a byte sized expression or not.
526 <item> If the expression is explicitly casted to a byte sized expression by
527 one of the '>', '<' or '^' operators, it is a byte expression.
528 <item> If this is not the case, and the expression contains a symbol,
529 explicitly declared as zero page symbol (by one of the .importzp or
530 .exportzp instructions), then the whole expression is assumed to be
532 <item> If the expression contains symbols that are not defined, and these
533 symbols are local symbols, the enclosing scopes are searched for a
534 symbol with the same name. If one exists and this symbol is defined,
535 it's attributes are used to determine the result size.
536 <item> In all other cases the expression is assumed to be word sized.
539 Note: If the assembler is not able to evaluate the expression at assembly
540 time, the linker will evaluate it and check for range errors as soon as
544 <sect1>Boolean expressions<p>
546 In the context of a boolean expression, any non zero value is evaluated as
547 true, any other value to false. The result of a boolean expression is 1 if
548 it's true, and zero if it's false. There are boolean operators with extreme
549 low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/
550 operators are shortcut operators. That is, if the result of the expression is
551 already known, after evaluating the left hand side, the right hand side is
555 <sect1>Constant expressions<p>
557 Sometimes an expression must evaluate to a constant without looking at any
558 further input. One such example is the <tt/<ref id=".IF" name=".IF">/ command
559 that decides if parts of the code are assembled or not. An expression used in
560 the <tt/.IF/ command cannot reference a symbol defined later, because the
561 decision about the <tt/.IF/ must be made at the point when it is read. If the
562 expression used in such a context contains only constant numerical values,
563 there is no problem. When unresolvable symbols are involved it may get harder
564 for the assembler to determine if the expression is actually constant, and it
565 is even possible to create expressions that aren't recognized as constant.
566 Simplifying the expressions will often help.
568 In cases where the result of the expression is not needed immediately, the
569 assembler will delay evaluation until all input is read, at which point all
570 symbols are known. So using arbitrary complex constant expressions is no
571 problem in most cases.
575 <sect1>Available operators<label id="operators"><p>
579 <bf/Operator/| <bf/Description/| <bf/Precedence/@<hline>
580 | Built-in string functions| 0@
582 | Built-in pseudo-variables| 1@
583 | Built-in pseudo-functions| 1@
584 +| Unary positive| 1@
585 -| Unary negative| 1@
587 .BITNOT| Unary bitwise not| 1@
589 .LOBYTE| Unary low-byte operator| 1@
591 .HIBYTE| Unary high-byte operator| 1@
593 .BANKBYTE| Unary bank-byte operator| 1@
595 *| Multiplication| 2@
597 .MOD| Modulo operator| 2@
599 .BITAND| Bitwise and| 2@
601 .BITXOR| Binary bitwise xor| 2@
603 .SHL| Shift-left operator| 2@
605 .SHR| Shift-right operator| 2@
607 +| Binary addition| 3@
608 -| Binary subtraction| 3@
610 .BITOR| Bitwise or| 3@
612 = | Compare operator (equal)| 4@
613 <>| Compare operator (not equal)| 4@
614 <| Compare operator (less)| 4@
615 >| Compare operator (greater)| 4@
616 <=| Compare operator (less or equal)| 4@
617 >=| Compare operator (greater or equal)| 4@
620 .AND| Boolean and| 5@
621 .XOR| Boolean xor| 5@
623 ||<newline>
627 .NOT| Boolean not| 7@<hline>
629 <caption>Available operators, sorted by precedence
632 To force a specific order of evaluation, parentheses may be used, as usual.
636 <sect>Symbols and labels<p>
638 A symbol or label is an identifier that starts with a letter and is followed
639 by letters and digits. Depending on some features enabled (see
640 <tt><ref id="at_in_identifiers" name="at_in_identifiers"></tt>,
641 <tt><ref id="dollar_in_identifiers" name="dollar_in_identifiers"></tt> and
642 <tt><ref id="leading_dot_in_identifiers" name="leading_dot_in_identifiers"></tt>)
643 other characters may be present. Use of identifiers consisting of a single
644 character will not work in all cases, because some of these identifiers are
645 reserved keywords (for example "A" is not a valid identifier for a label,
646 because it is the keyword for the accumulator).
648 The assembler allows you to use symbols instead of naked values to make
649 the source more readable. There are a lot of different ways to define and
650 use symbols and labels, giving a lot of flexibility.
652 <sect1>Numeric constants<p>
654 Numeric constants are defined using the equal sign or the label assignment
655 operator. After doing
661 may use the symbol "two" in every place where a number is expected, and it is
662 evaluated to the value 2 in this context. The label assignment operator causes
663 the same, but causes the symbol to be marked as a label, which may cause a
664 different handling in the debugger:
670 The right side can of course be an expression:
677 <sect1>Standard labels<p>
679 A label is defined by writing the name of the label at the start of the line
680 (before any instruction mnemonic, macro or pseudo directive), followed by a
681 colon. This will declare a symbol with the given name and the value of the
682 current program counter.
685 <sect1>Local labels and symbols<p>
687 Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to
688 create regions of code where the names of labels and symbols are local to this
689 region. They are not known outside of this region and cannot be accessed from
690 there. Such regions may be nested like PROCEDUREs in Pascal.
692 See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
693 directive for more information.
696 <sect1>Cheap local labels<p>
698 Cheap local labels are defined like standard labels, but the name of the
699 label must begin with a special symbol (usually '@', but this can be
700 changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt>
703 Cheap local labels are visible only between two non cheap labels. As soon as a
704 standard symbol is encountered (this may also be a local symbol if inside a
705 region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the
706 cheap local symbol goes out of scope.
708 You may use cheap local labels as an easy way to reuse common label
709 names like "Loop". Here is an example:
712 Clear: lda #$00 ; Global label
714 @Loop: sta Mem,y ; Local label
718 Sub: ... ; New global label
719 bne @Loop ; ERROR: Unknown identifier!
722 <sect1>Unnamed labels<p>
724 If you really want to write messy code, there are also unnamed labels. These
725 labels do not have a name (you guessed that already, didn't you?). A colon is
726 used to mark the absence of the name.
728 Unnamed labels may be accessed by using the colon plus several minus or plus
729 characters as a label designator. Using the '-' characters will create a back
730 reference (use the n'th label backwards), using '+' will create a forward
731 reference (use the n'th label in forward direction). An example will help to
754 As you can see from the example, unnamed labels will make even short
755 sections of code hard to understand, because you have to count labels
756 to find branch targets (this is the reason why I for my part do
757 prefer the "cheap" local labels). Nevertheless, unnamed labels are
758 convenient in some situations, so it's your decision.
761 <sect1>Using macros to define labels and constants<p>
763 While there are drawbacks with this approach, it may be handy in some
764 situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is
765 possible to define symbols or constants that may be used elsewhere. Since
766 the macro facility works on a very low level, there is no scoping. On the
767 other side, you may also define string constants this way (this is not
768 possible with the other symbol types).
774 .DEFINE version "SOS V2.3"
776 four = two * two ; Ok
779 .PROC ; Start local scope
780 two = 3 ; Will give "2 = 3" - invalid!
785 <sect1>Symbols and <tt>.DEBUGINFO</tt><p>
787 If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref
788 id="option-g" name="-g"> is given on the command line), global, local and
789 cheap local labels are written to the object file and will be available in the
790 symbol file via the linker. Unnamed labels are not written to the object file,
791 because they don't have a name which would allow to access them.
795 <sect>Scopes<label id="scopes"><p>
797 ca65 implements several sorts of scopes for symbols.
799 <sect1>Global scope<p>
801 All (non cheap local) symbols that are declared outside of any nested scopes
805 <sect1>Cheap locals<p>
807 A special scope is the scope for cheap local symbols. It lasts from one non
808 local symbol to the next one, without any provisions made by the programmer.
809 All other scopes differ in usage but use the same concept internally.
812 <sect1>Generic nested scopes<p>
814 A nested scoped for generic use is started with <tt/<ref id=".SCOPE"
815 name=".SCOPE">/ and closed with <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/.
816 The scope can have a name, in which case it is accessible from the outside by
817 using <ref id="scopesyntax" name="explicit scopes">. If the scope does not
818 have a name, all symbols created within the scope are local to the scope, and
819 aren't accessible from the outside.
821 A nested scope can access symbols from the local or from enclosing scopes by
822 name without using explicit scope names. In some cases there may be
823 ambiguities, for example if there is a reference to a local symbol that is not
824 yet defined, but a symbol with the same name exists in outer scopes:
836 In the example above, the <tt/lda/ instruction will load the value 3 into the
837 accumulator, because <tt/foo/ is redefined in the scope. However:
849 Here, <tt/lda/ will still load from <tt/$12,x/, but since it is unknown to the
850 assembler that <tt/foo/ is a zeropage symbol when translating the instruction,
851 absolute mode is used instead. In fact, the assembler will not use absolute
852 mode by default, but it will search through the enclosing scopes for a symbol
853 with the given name. If one is found, the address size of this symbol is used.
854 This may lead to errors:
866 In this case, when the assembler sees the symbol <tt/foo/ in the <tt/lda/
867 instruction, it will search for an already defined symbol <tt/foo/. It will
868 find <tt/foo/ in scope <tt/outer/, and a close look reveals that it is a
869 zeropage symbol. So the assembler will use zeropage addressing mode. If
870 <tt/foo/ is redefined later in scope <tt/inner/, the assembler tries to change
871 the address in the <tt/lda/ instruction already translated, but since the new
872 value needs absolute addressing mode, this fails, and an error message "Range
875 Of course the most simple solution for the problem is to move the definition
876 of <tt/foo/ in scope <tt/inner/ upwards, so it precedes its use. There may be
877 rare cases when this cannot be done. In these cases, you can use one of the
878 address size override operators:
890 This will cause the <tt/lda/ instruction to be translated using absolute
891 addressing mode, which means changing the symbol reference later does not
895 <sect1>Nested procedures<p>
897 A nested procedure is created by use of <tt/<ref id=".PROC" name=".PROC">/. It
898 differs from a <tt/<ref id=".SCOPE" name=".SCOPE">/ in that it must have a
899 name, and a it will introduce a symbol with this name in the enclosing scope.
908 is actually the same as
917 This is the reason why a procedure must have a name. If you want a scope
918 without a name, use <tt/<ref id=".SCOPE" name=".SCOPE">/.
920 <bf/Note:/ As you can see from the example above, scopes and symbols live in
921 different namespaces. There can be a symbol named <tt/foo/ and a scope named
922 <tt/foo/ without any conflicts (but see the section titled <ref
923 id="scopesearch" name=""Scope search order"">).
926 <sect1>Structs, unions and enums<p>
928 Structs, unions and enums are explained in a <ref id="structs" name="separate
929 section">, I do only cover them here, because if they are declared with a
930 name, they open a nested scope, similar to <tt/<ref id=".SCOPE"
931 name=".SCOPE">/. However, when no name is specified, the behaviour is
932 different: In this case, no new scope will be opened, symbols declared within
933 a struct, union, or enum declaration will then be added to the enclosing scope
937 <sect1>Explicit scope specification<label id="scopesyntax"><p>
939 Accessing symbols from other scopes is possible by using an explicit scope
940 specification, provided that the scope where the symbol lives in has a name.
941 The namespace token (<tt/::/) is used to access other scopes:
949 lda foo::bar ; Access foo in scope bar
952 The only way to deny access to a scope from the outside is to declare a scope
953 without a name (using the <tt/<ref id=".SCOPE" name=".SCOPE">/ command).
955 A special syntax is used to specify the global scope: If a symbol or scope is
956 preceded by the namespace token, the global scope is searched:
963 lda #::bar ; Access the global bar (which is 3)
968 <sect1>Scope search order<label id="scopesearch"><p>
970 The assembler searches for a scope in a similar way as for a symbol. First, it
971 looks in the current scope, and then it walks up the enclosing scopes until
974 However, one important thing to note when using explicit scope syntax is, that
975 a symbol may be accessed before it is defined, but a scope may <bf/not/ be
976 used without a preceding definition. This means that in the following
985 lda #foo::bar ; Will load 3, not 2!
992 the reference to the scope <tt/foo/ will use the global scope, and not the
993 local one, because the local one is not visible at the point where it is
996 Things get more complex if a complete chain of scopes is specified:
1007 lda #outer::inner::bar ; 1
1019 When <tt/outer::inner::bar/ is referenced in the <tt/lda/ instruction, the
1020 assembler will first search in the local scope for a scope named <tt/outer/.
1021 Since none is found, the enclosing scope (<tt/another/) is checked. There is
1022 still no scope named <tt/outer/, so scope <tt/foo/ is checked, and finally
1023 scope <tt/outer/ is found. Within this scope, <tt/inner/ is searched, and in
1024 this scope, the assembler looks for a symbol named <tt/bar/.
1026 Please note that once the anchor scope is found, all following scopes
1027 (<tt/inner/ in this case) are expected to be found exactly in this scope. The
1028 assembler will search the scope tree only for the first scope (if it is not
1029 anchored in the root scope). Starting from there on, there is no flexibility,
1030 so if the scope named <tt/outer/ found by the assembler does not contain a
1031 scope named <tt/inner/, this would be an error, even if such a pair does exist
1032 (one level up in global scope).
1034 Ambiguities that may be introduced by this search algorithm may be removed by
1035 anchoring the scope specification in the global scope. In the example above,
1036 if you want to access the "other" symbol <tt/bar/, you would have to write:
1047 lda #::outer::inner::bar ; 2
1060 <sect>Address sizes and memory models<label id="address-sizes"><p>
1062 <sect1>Address sizes<p>
1064 ca65 assigns each segment and each symbol an address size. This is true, even
1065 if the symbol is not used as an address. You may also think of a value range
1066 of the symbol instead of an address size.
1068 Possible address sizes are:
1071 <item>Zeropage or direct (8 bits)
1072 <item>Absolute (16 bits)
1074 <item>Long (32 bits)
1077 Since the assembler uses default address sizes for the segments and symbols,
1078 it is usually not necessary to override the default behaviour. In cases, where
1079 it is necessary, the following keywords may be used to specify address sizes:
1082 <item>DIRECT, ZEROPAGE or ZP for zeropage addressing (8 bits).
1083 <item>ABSOLUTE, ABS or NEAR for absolute addressing (16 bits).
1084 <item>FAR for far addressing (24 bits).
1085 <item>LONG or DWORD for long addressing (32 bits).
1089 <sect1>Address sizes of segments<p>
1091 The assembler assigns an address size to each segment. Since the
1092 representation of a label within this segment is "segment start + offset",
1093 labels will inherit the address size of the segment they are declared in.
1095 The address size of a segment may be changed, by using an optional address
1096 size modifier. See the <tt/<ref id=".SEGMENT" name="segment directive">/ for
1097 an explanation on how this is done.
1100 <sect1>Address sizes of symbols<p>
1105 <sect1>Memory models<p>
1107 The default address size of a segment depends on the memory model used. Since
1108 labels inherit the address size from the segment they are declared in,
1109 changing the memory model is an easy way to change the address size of many
1115 <sect>Pseudo variables<label id="pseudo-variables"><p>
1117 Pseudo variables are readable in all cases, and in some special cases also
1120 <sect1><tt>*</tt><p>
1122 Reading this pseudo variable will return the program counter at the start
1123 of the current input line.
1125 Assignment to this variable is possible when <tt/<ref id=".FEATURE"
1126 name=".FEATURE pc_assignment">/ is used. Note: You should not use
1127 assignments to <tt/*/, use <tt/<ref id=".ORG" name=".ORG">/ instead.
1130 <sect1><tt>.CPU</tt><label id=".CPU"><p>
1132 Reading this pseudo variable will give a constant integer value that
1133 tells which CPU is currently enabled. It can also tell which instruction
1134 set the CPU is able to translate. The value read from the pseudo variable
1135 should be further examined by using one of the constants defined by the
1136 "cpu" macro package (see <tt/<ref id=".MACPACK" name=".MACPACK">/).
1138 It may be used to replace the .IFPxx pseudo instructions or to construct
1139 even more complex expressions.
1145 .if (.cpu .bitand CPU_ISET_65816)
1157 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
1159 This builtin pseudo variable is only available in macros. It is replaced by
1160 the actual number of parameters that were given in the macro invocation.
1165 .macro foo arg1, arg2, arg3
1166 .if .paramcount <> 3
1167 .error "Too few parameters for macro foo"
1173 See section <ref id="macros" name="Macros">.
1176 <sect1><tt>.TIME</tt><label id=".TIME"><p>
1178 Reading this pseudo variable will give a constant integer value that
1179 represents the current time in POSIX standard (as seconds since the
1182 It may be used to encode the time of translation somewhere in the created
1188 .dword .time ; Place time here
1192 <sect1><tt>.VERSION</tt><label id=".VERSION"><p>
1194 Reading this pseudo variable will give the assembler version according to
1195 the following formula:
1197 VER_MAJOR*$100 + VER_MINOR*$10 + VER_PATCH
1199 It may be used to encode the assembler version or check the assembler for
1200 special features not available with older versions.
1204 Version 2.11.1 of the assembler will return $2B1 as numerical constant when
1205 reading the pseudo variable <tt/.VERSION/.
1209 <sect>Pseudo functions<label id="pseudo-functions"><p>
1211 Pseudo functions expect their arguments in parenthesis, and they have a result,
1212 either a string or an expression.
1215 <sect1><tt>.BANKBYTE</tt><label id=".BANKBYTE"><p>
1217 The function returns the bank byte (that is, bits 16-23) of its argument.
1218 It works identical to the '^' operator.
1220 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1221 <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>
1224 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
1226 Builtin function. The function evaluates its argument in braces and yields
1227 "false" if the argument is non blank (there is an argument), and "true" if
1228 there is no argument. The token list that makes up the function argument
1229 may optionally be enclosed in curly braces. This allows the inclusion of
1230 tokens that would otherwise terminate the list (the closing right
1231 parenthesis). The curly braces are not considered part of the list, a list
1232 just consisting of curly braces is considered to be empty.
1234 As an example, the <tt/.IFBLANK/ statement may be replaced by
1242 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
1244 Builtin string function. The function allows to concatenate a list of string
1245 constants separated by commas. The result is a string constant that is the
1246 concatenation of all arguments. This function is most useful in macros and
1247 when used together with the <tt/.STRING/ builtin function. The function may
1248 be used in any case where a string constant is expected.
1253 .include .concat ("myheader", ".", "inc")
1256 This is the same as the command
1259 .include "myheader.inc"
1263 <sect1><tt>.CONST</tt><label id=".CONST"><p>
1265 Builtin function. The function evaluates its argument in braces and
1266 yields "true" if the argument is a constant expression (that is, an
1267 expression that yields a constant value at assembly time) and "false"
1268 otherwise. As an example, the .IFCONST statement may be replaced by
1275 <sect1><tt>.HIBYTE</tt><label id=".HIBYTE"><p>
1277 The function returns the high byte (that is, bits 8-15) of its argument.
1278 It works identical to the '>' operator.
1280 See: <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>,
1281 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1284 <sect1><tt>.HIWORD</tt><label id=".HIWORD"><p>
1286 The function returns the high word (that is, bits 16-31) of its argument.
1288 See: <tt><ref id=".LOWORD" name=".LOWORD"></tt>
1291 <sect1><tt>.IDENT</tt><label id=".IDENT"><p>
1293 The function expects a string as its argument, and converts this argument
1294 into an identifier. If the string starts with the current <tt/<ref
1295 id=".LOCALCHAR" name=".LOCALCHAR">/, it will be converted into a cheap local
1296 identifier, otherwise it will be converted into a normal identifier.
1301 .macro makelabel arg1, arg2
1302 .ident (.concat (arg1, arg2)):
1305 makelabel "foo", "bar"
1307 .word foobar ; Valid label
1311 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1313 Builtin function. Extracts the left part of a given token list.
1318 .LEFT (<int expr>, <token list>)
1321 The first integer expression gives the number of tokens to extract from
1322 the token list. The second argument is the token list itself. The token
1323 list may optionally be enclosed into curly braces. This allows the
1324 inclusion of tokens that would otherwise terminate the list (the closing
1325 right paren in the given case).
1329 To check in a macro if the given argument has a '#' as first token
1330 (immediate addressing mode), use something like this:
1335 .if (.match (.left (1, {arg}), #))
1337 ; ldax called with immediate operand
1345 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1346 name=".RIGHT"></tt> builtin functions.
1349 <sect1><tt>.LOBYTE</tt><label id=".LOBYTE"><p>
1351 The function returns the low byte (that is, bits 0-7) of its argument.
1352 It works identical to the '<' operator.
1354 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1355 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1358 <sect1><tt>.LOWORD</tt><label id=".LOWORD"><p>
1360 The function returns the low word (that is, bits 0-15) of its argument.
1362 See: <tt><ref id=".HIWORD" name=".HIWORD"></tt>
1365 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1367 Builtin function. Matches two token lists against each other. This is
1368 most useful within macros, since macros are not stored as strings, but
1374 .MATCH(<token list #1>, <token list #2>)
1377 Both token list may contain arbitrary tokens with the exception of the
1378 terminator token (comma resp. right parenthesis) and
1385 The token lists may optionally be enclosed into curly braces. This allows
1386 the inclusion of tokens that would otherwise terminate the list (the closing
1387 right paren in the given case). Often a macro parameter is used for any of
1390 Please note that the function does only compare tokens, not token
1391 attributes. So any number is equal to any other number, regardless of the
1392 actual value. The same is true for strings. If you need to compare tokens
1393 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1394 name=".XMATCH"></tt> function.
1398 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1399 while honoring the sign bit. The builtin processor instructions will allow
1400 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1401 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1402 to check for this and print and error for invalid calls.
1407 .if (.not .blank(arg)) .and (.not .match ({arg}, a))
1408 .error "Syntax error"
1411 cmp #$80 ; Bit 7 into carry
1412 lsr a ; Shift carry into bit 7
1417 The macro will only accept no arguments, or one argument that must be the
1418 reserved keyword "A".
1420 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1423 <sect1><tt>.MAX</tt><label id=".MAX"><p>
1425 Builtin function. The result is the larger of two values.
1430 .MAX (<value #1>, <value #2>)
1436 ; Reserve space for the larger of two data blocks
1437 savearea: .max (.sizeof (foo), .sizeof (bar))
1440 See: <tt><ref id=".MIN" name=".MIN"></tt>
1443 <sect1><tt>.MID</tt><label id=".MID"><p>
1445 Builtin function. Takes a starting index, a count and a token list as
1446 arguments. Will return part of the token list.
1451 .MID (<int expr>, <int expr>, <token list>)
1454 The first integer expression gives the starting token in the list (the first
1455 token has index 0). The second integer expression gives the number of tokens
1456 to extract from the token list. The third argument is the token list itself.
1457 The token list may optionally be enclosed into curly braces. This allows the
1458 inclusion of tokens that would otherwise terminate the list (the closing
1459 right paren in the given case).
1463 To check in a macro if the given argument has a '<tt/#/' as first token
1464 (immediate addressing mode), use something like this:
1469 .if (.match (.mid (0, 1, {arg}), #))
1471 ; ldax called with immediate operand
1479 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1480 name=".RIGHT"></tt> builtin functions.
1483 <sect1><tt>.MIN</tt><label id=".MIN"><p>
1485 Builtin function. The result is the smaller of two values.
1490 .MIN (<value #1>, <value #2>)
1496 ; Reserve space for some data, but 256 bytes minimum
1497 savearea: .min (.sizeof (foo), 256)
1500 See: <tt><ref id=".MAX" name=".MAX"></tt>
1503 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
1505 Builtin function. The function expects an identifier as argument in braces.
1506 The argument is evaluated, and the function yields "true" if the identifier
1507 is a symbol that has already been referenced somewhere in the source file up
1508 to the current position. Otherwise the function yields false. As an example,
1509 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
1515 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1518 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
1520 Builtin function. Extracts the right part of a given token list.
1525 .RIGHT (<int expr>, <token list>)
1528 The first integer expression gives the number of tokens to extract from the
1529 token list. The second argument is the token list itself. The token list
1530 may optionally be enclosed into curly braces. This allows the inclusion of
1531 tokens that would otherwise terminate the list (the closing right paren in
1534 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
1535 name=".MID"></tt> builtin functions.
1538 <sect1><tt>.SIZEOF</tt><label id=".SIZEOF"><p>
1540 <tt/.SIZEOF/ is a pseudo function that returns the size of its argument. The
1541 argument can be a struct/union, a struct member, a procedure, or a label. In
1542 case of a procedure or label, its size is defined by the amount of data
1543 placed in the segment where the label is relative to. If a line of code
1544 switches segments (for example in a macro) data placed in other segments
1545 does not count for the size.
1547 Please note that a symbol or scope must exist, before it is used together with
1548 <tt/.SIZEOF/ (this may get relaxed later, but will always be true for scopes).
1549 A scope has preference over a symbol with the same name, so if the last part
1550 of a name represents both, a scope and a symbol, the scope is chosen over the
1553 After the following code:
1556 .struct Point ; Struct size = 4
1561 P: .tag Point ; Declare a point
1562 @P: .tag Point ; Declare another point
1574 .data ; Segment switch!!!
1580 <tag><tt/.sizeof(Point)/</tag>
1581 will have the value 4, because this is the size of struct <tt/Point/.
1583 <tag><tt/.sizeof(Point::xcoord)/</tag>
1584 will have the value 2, because this is the size of the member <tt/xcoord/
1585 in struct <tt/Point/.
1587 <tag><tt/.sizeof(P)/</tag>
1588 will have the value 4, this is the size of the data declared on the same
1589 source line as the label <tt/P/, which is in the same segment that <tt/P/
1592 <tag><tt/.sizeof(@P)/</tag>
1593 will have the value 4, see above. The example demonstrates that <tt/.SIZEOF/
1594 does also work for cheap local symbols.
1596 <tag><tt/.sizeof(Code)/</tag>
1597 will have the value 3, since this is amount of data emitted into the code
1598 segment, the segment that was active when <tt/Code/ was entered. Note that
1599 this value includes the amount of data emitted in child scopes (in this
1600 case <tt/Code::Inner/).
1602 <tag><tt/.sizeof(Code::Inner)/</tag>
1603 will have the value 1 as expected.
1605 <tag><tt/.sizeof(Data)/</tag>
1606 will have the value 0. Data is emitted within the scope <tt/Data/, but since
1607 the segment is switched after entry, this data is emitted into another
1612 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
1614 Builtin function. The function accepts a string and an index as
1615 arguments and returns the value of the character at the given position
1616 as an integer value. The index is zero based.
1622 ; Check if the argument string starts with '#'
1623 .if (.strat (Arg, 0) = '#')
1630 <sect1><tt>.SPRINTF</tt><label id=".SPRINTF"><p>
1632 Builtin function. It expects a format string as first argument. The number
1633 and type of the following arguments depend on the format string. The format
1634 string is similar to the one of the C <tt/printf/ function. Missing things
1635 are: Length modifiers, variable width.
1637 The result of the function is a string.
1644 ; Generate an identifier:
1645 .ident (.sprintf ("%s%03d", "label", num)):
1649 <sect1><tt>.STRING</tt><label id=".STRING"><p>
1651 Builtin function. The function accepts an argument in braces and converts
1652 this argument into a string constant. The argument may be an identifier, or
1653 a constant numeric value.
1655 Since you can use a string in the first place, the use of the function may
1656 not be obvious. However, it is useful in macros, or more complex setups.
1661 ; Emulate other assemblers:
1663 .segment .string(name)
1668 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
1670 Builtin function. The function accepts a string argument in braces and
1671 evaluates to the length of the string.
1675 The following macro encodes a string as a pascal style string with
1676 a leading length byte.
1680 .byte .strlen(Arg), Arg
1685 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
1687 Builtin function. The function accepts a token list in braces. The function
1688 result is the number of tokens given as argument. The token list may
1689 optionally be enclosed into curly braces which are not considered part of
1690 the list and not counted. Enclosement in curly braces allows the inclusion
1691 of tokens that would otherwise terminate the list (the closing right paren
1696 The <tt/ldax/ macro accepts the '#' token to denote immediate addressing (as
1697 with the normal 6502 instructions). To translate it into two separate 8 bit
1698 load instructions, the '#' token has to get stripped from the argument:
1702 .if (.match (.mid (0, 1, {arg}), #))
1703 ; ldax called with immediate operand
1704 lda #<(.right (.tcount ({arg})-1, {arg}))
1705 ldx #>(.right (.tcount ({arg})-1, {arg}))
1713 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
1715 Builtin function. Matches two token lists against each other. This is
1716 most useful within macros, since macros are not stored as strings, but
1722 .XMATCH(<token list #1>, <token list #2>)
1725 Both token list may contain arbitrary tokens with the exception of the
1726 terminator token (comma resp. right parenthesis) and
1733 The token lists may optionally be enclosed into curly braces. This allows
1734 the inclusion of tokens that would otherwise terminate the list (the closing
1735 right paren in the given case). Often a macro parameter is used for any of
1738 The function compares tokens <em/and/ token values. If you need a function
1739 that just compares the type of tokens, have a look at the <tt><ref
1740 id=".MATCH" name=".MATCH"></tt> function.
1742 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
1746 <sect>Control commands<label id="control-commands"><p>
1748 Here's a list of all control commands and a description, what they do:
1751 <sect1><tt>.A16</tt><label id=".A16"><p>
1753 Valid only in 65816 mode. Switch the accumulator to 16 bit.
1755 Note: This command will not emit any code, it will tell the assembler to
1756 create 16 bit operands for immediate accumulator addressing mode.
1758 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1761 <sect1><tt>.A8</tt><label id=".A8"><p>
1763 Valid only in 65816 mode. Switch the accumulator to 8 bit.
1765 Note: This command will not emit any code, it will tell the assembler to
1766 create 8 bit operands for immediate accu addressing mode.
1768 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1771 <sect1><tt>.ADDR</tt><label id=".ADDR"><p>
1773 Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and
1774 may be used for better readability if the data words are address values. In
1775 65816 mode, the address is forced to be 16 bit wide to fit into the current
1776 segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command
1777 must be followed by a sequence of (not necessarily constant) expressions.
1782 .addr $0D00, $AF13, _Clear
1785 See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD"
1789 <sect1><tt>.ALIGN</tt><label id=".ALIGN"><p>
1791 Align data to a given boundary. The command expects a constant integer
1792 argument that must be a power of two, plus an optional second argument
1793 in byte range. If there is a second argument, it is used as fill value,
1794 otherwise the value defined in the linker configuration file is used
1795 (the default for this value is zero).
1797 Since alignment depends on the base address of the module, you must
1798 give the same (or a greater) alignment for the segment when linking.
1799 The linker will give you a warning, if you don't do that.
1808 <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"><p>
1810 Define a string with a trailing zero.
1815 Msg: .asciiz "Hello world"
1818 This will put the string "Hello world" followed by a binary zero into
1819 the current segment. There may be more strings separated by commas, but
1820 the binary zero is only appended once (after the last one).
1823 <sect1><tt>.ASSERT</tt><label id=".ASSERT"><p>
1825 Add an assertion. The command is followed by an expression, an action
1826 specifier, and an optional message that is output in case the assertion
1827 fails. If no message was given, the string "Assertion failed" is used. The
1828 action specifier may be one of <tt/warning/, <tt/error/, <tt/ldwarning/ or
1829 <tt/lderror/. In the former two cases, the assertion is evaluated by the
1830 assembler if possible, and in any case, it's also passed to the linker in
1831 the object file (if one is generated). The linker will then evaluate the
1832 expression when segment placement has been done.
1837 .assert * = $8000, error, "Code not at $8000"
1840 The example assertion will check that the current location is at $8000,
1841 when the output file is written, and abort with an error if this is not
1842 the case. More complex expressions are possible. The action specifier
1843 <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs
1844 an error message. In the latter case, generation of the output file is
1845 suppressed in both the assembler and linker.
1848 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
1850 Is followed by a plus or a minus character. When switched on (using a
1851 +), undefined symbols are automatically marked as import instead of
1852 giving errors. When switched off (which is the default so this does not
1853 make much sense), this does not happen and an error message is
1854 displayed. The state of the autoimport flag is evaluated when the
1855 complete source was translated, before outputting actual code, so it is
1856 <em/not/ possible to switch this feature on or off for separate sections
1857 of code. The last setting is used for all symbols.
1859 You should probably not use this switch because it delays error
1860 messages about undefined symbols until the link stage. The cc65
1861 compiler (which is supposed to produce correct assembler code in all
1862 circumstances, something which is not true for most assembler
1863 programmers) will insert this command to avoid importing each and every
1864 routine from the runtime library.
1869 .autoimport + ; Switch on auto import
1872 <sect1><tt>.BANKBYTES</tt><label id=".BANKBYTES"><p>
1874 Define byte sized data by extracting only the bank byte (that is, bits 16-23) from
1875 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
1876 the operator '^' prepended to each expression in its list.
1881 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
1883 TableLookupLo: .lobytes MyTable
1884 TableLookupHi: .hibytes MyTable
1885 TableLookupBank: .bankbytes MyTable
1888 which is equivalent to
1891 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
1892 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
1893 TableLookupBank: .byte ^TableItem0, ^TableItem1, ^TableItem2, ^TableItem3
1896 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
1897 <tt><ref id=".HIBYTES" name=".HIBYTES"></tt>,
1898 <tt><ref id=".LOBYTES" name=".LOBYTES"></tt>
1901 <sect1><tt>.BSS</tt><label id=".BSS"><p>
1903 Switch to the BSS segment. The name of the BSS segment is always "BSS",
1904 so this is a shortcut for
1910 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1913 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
1915 Define byte sized data. Must be followed by a sequence of (byte ranged)
1916 expressions or strings.
1922 .byt "world", $0D, $00
1926 <sect1><tt>.CASE</tt><label id=".CASE"><p>
1928 Switch on or off case sensitivity on identifiers. The default is off
1929 (that is, identifiers are case sensitive), but may be changed by the
1930 -i switch on the command line.
1931 The command must be followed by a '+' or '-' character to switch the
1932 option on or off respectively.
1937 .case - ; Identifiers are not case sensitive
1941 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
1943 Apply a custom mapping for characters. The command is followed by two
1944 numbers in the range 1..255. The first one is the index of the source
1945 character, the second one is the mapping. The mapping applies to all
1946 character and string constants when they generate output, and overrides
1947 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
1948 command line switch.
1953 .charmap $41, $61 ; Map 'A' to 'a'
1957 <sect1><tt>.CODE</tt><label id=".CODE"><p>
1959 Switch to the CODE segment. The name of the CODE segment is always
1960 "CODE", so this is a shortcut for
1966 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1969 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
1971 Export a symbol and mark it in a special way. The linker is able to build
1972 tables of all such symbols. This may be used to automatically create a list
1973 of functions needed to initialize linked library modules.
1975 Note: The linker has a feature to build a table of marked routines, but it
1976 is your code that must call these routines, so just declaring a symbol with
1977 <tt/.CONDES/ does nothing by itself.
1979 All symbols are exported as an absolute (16 bit) symbol. You don't need to
1980 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
1981 is implied by <tt/.CONDES/.
1983 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
1984 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
1985 specifying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
1986 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
1987 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
1988 name=".INTERRUPTOR"></tt> commands are actually shortcuts for <tt/.CONDES/
1989 with a type of <tt/constructor/ resp. <tt/destructor/ or <tt/interruptor/.
1991 After the type, an optional priority may be specified. Higher numeric values
1992 mean higher priority. If no priority is given, the default priority of 7 is
1993 used. Be careful when assigning priorities to your own module constructors
1994 so they won't interfere with the ones in the cc65 library.
1999 .condes ModuleInit, constructor
2000 .condes ModInit, 0, 16
2003 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
2004 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
2005 name=".INTERRUPTOR"></tt> commands and the separate section <ref id="condes"
2006 name="Module constructors/destructors"> explaining the feature in more
2010 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
2012 Export a symbol and mark it as a module constructor. This may be used
2013 together with the linker to build a table of constructor subroutines that
2014 are called by the startup code.
2016 Note: The linker has a feature to build a table of marked routines, but it
2017 is your code that must call these routines, so just declaring a symbol as
2018 constructor does nothing by itself.
2020 A constructor is always exported as an absolute (16 bit) symbol. You don't
2021 need to use an additional <tt/.export/ statement, this is implied by
2022 <tt/.constructor/. It may have an optional priority that is separated by a
2023 comma. Higher numeric values mean a higher priority. If no priority is
2024 given, the default priority of 7 is used. Be careful when assigning
2025 priorities to your own module constructors so they won't interfere with the
2026 ones in the cc65 library.
2031 .constructor ModuleInit
2032 .constructor ModInit, 16
2035 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
2036 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
2037 <ref id="condes" name="Module constructors/destructors"> explaining the
2038 feature in more detail.
2041 <sect1><tt>.DATA</tt><label id=".DATA"><p>
2043 Switch to the DATA segment. The name of the DATA segment is always
2044 "DATA", so this is a shortcut for
2050 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2053 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
2055 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
2056 create word sized data in native 65XX format). Must be followed by a
2057 sequence of (word ranged) expressions.
2065 This will emit the bytes
2071 into the current segment in that order.
2074 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
2076 Switch on or off debug info generation. The default is off (that is,
2077 the object file will not contain debug infos), but may be changed by the
2078 -g switch on the command line.
2079 The command must be followed by a '+' or '-' character to switch the
2080 option on or off respectively.
2085 .debuginfo + ; Generate debug info
2089 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
2091 Start a define style macro definition. The command is followed by an
2092 identifier (the macro name) and optionally by a list of formal arguments
2094 See section <ref id="macros" name="Macros">.
2097 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
2099 Builtin function. The function expects an identifier as argument in braces.
2100 The argument is evaluated, and the function yields "true" if the identifier
2101 is a symbol that is already defined somewhere in the source file up to the
2102 current position. Otherwise the function yields false. As an example, the
2103 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
2110 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
2112 Export a symbol and mark it as a module destructor. This may be used
2113 together with the linker to build a table of destructor subroutines that
2114 are called by the startup code.
2116 Note: The linker has a feature to build a table of marked routines, but it
2117 is your code that must call these routines, so just declaring a symbol as
2118 constructor does nothing by itself.
2120 A destructor is always exported as an absolute (16 bit) symbol. You don't
2121 need to use an additional <tt/.export/ statement, this is implied by
2122 <tt/.destructor/. It may have an optional priority that is separated by a
2123 comma. Higher numerical values mean a higher priority. If no priority is
2124 given, the default priority of 7 is used. Be careful when assigning
2125 priorities to your own module destructors so they won't interfere with the
2126 ones in the cc65 library.
2131 .destructor ModuleDone
2132 .destructor ModDone, 16
2135 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
2136 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
2137 section <ref id="condes" name="Module constructors/destructors"> explaining
2138 the feature in more detail.
2141 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
2143 Define dword sized data (4 bytes) Must be followed by a sequence of
2149 .dword $12344512, $12FA489
2153 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
2155 Conditional assembly: Reverse the current condition.
2158 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
2160 Conditional assembly: Reverse current condition and test a new one.
2163 <sect1><tt>.END</tt><label id=".END"><p>
2165 Forced end of assembly. Assembly stops at this point, even if the command
2166 is read from an include file.
2169 <sect1><tt>.ENDENUM</tt><label id=".ENDENUM"><p>
2171 End a <tt><ref id=".ENUM" name=".ENUM"></tt> declaration.
2174 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
2176 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
2177 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
2180 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
2182 End of macro definition (see section <ref id="macros" name="Macros">).
2185 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
2187 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
2190 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
2192 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
2195 <sect1><tt>.ENDSCOPE</tt><label id=".ENDSCOPE"><p>
2197 End of local lexical level (see <tt/<ref id=".SCOPE" name=".SCOPE">/).
2200 <sect1><tt>.ENDSTRUCT</tt><label id=".ENDSTRUCT"><p>
2202 Ends a struct definition. See the <tt/<ref id=".STRUCT" name=".STRUCT">/
2203 command and the separate section named <ref id="structs" name=""Structs
2207 <sect1><tt>.ENUM</tt><label id=".ENUM"><p>
2209 Start an enumeration. This directive is very similar to the C <tt/enum/
2210 keyword. If a name is given, a new scope is created for the enumeration,
2211 otherwise the enumeration members are placed in the enclosing scope.
2213 In the enumeration body, symbols are declared. The first symbol has a value
2214 of zero, and each following symbol will get the value of the preceding plus
2215 one. This behaviour may be overridden by an explicit assignment. Two symbols
2216 may have the same value.
2228 Above example will create a new scope named <tt/errorcodes/ with three
2229 symbols in it that get the values 0, 1 and 2 respectively. Another way
2230 to write this would have been:
2240 Please note that explicit scoping must be used to access the identifiers:
2243 .word errorcodes::no_error
2246 A more complex example:
2255 EWOULDBLOCK = EAGAIN
2259 In this example, the enumeration does not have a name, which means that the
2260 members will be visible in the enclosing scope and can be used in this scope
2261 without explicit scoping. The first member (<tt/EUNKNOWN/) has the value -1.
2262 The value for the following members is incremented by one, so <tt/EOK/ would
2263 be zero and so on. <tt/EWOULDBLOCK/ is an alias for <tt/EGAIN/, so it has an
2264 override for the value using an already defined symbol.
2267 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
2269 Force an assembly error. The assembler will output an error message
2270 preceded by "User error" and will <em/not/ produce an object file.
2272 This command may be used to check for initial conditions that must be
2273 set before assembling a source file.
2283 .error "Must define foo or bar!"
2287 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
2288 id=".OUT" name=".OUT"></tt> directives.
2291 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
2293 Abort a macro expansion immediately. This command is often useful in
2294 recursive macros. See separate section <ref id="macros" name="Macros">.
2297 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
2299 Make symbols accessible from other modules. Must be followed by a comma
2300 separated list of symbols to export, with each one optionally followed by an
2301 address specification and (also optional) an assignment. Using an additional
2302 assignment in the export statement allows to define and export a symbol in
2303 one statement. The default is to export the symbol with the address size it
2304 actually has. The assembler will issue a warning, if the symbol is exported
2305 with an address size smaller than the actual address size.
2312 .export foobar: far = foo * bar
2313 .export baz := foobar, zap: far = baz - bar
2316 As with constant definitions, using <tt/:=/ instead of <tt/=/ marks the
2319 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
2322 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
2324 Make symbols accessible from other modules. Must be followed by a comma
2325 separated list of symbols to export. The exported symbols are explicitly
2326 marked as zero page symbols. An assignment may be included in the
2327 <tt/.EXPORTZP/ statement. This allows to define and export a symbol in one
2334 .exportzp baz := $02
2337 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
2340 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
2342 Define far (24 bit) address data. The command must be followed by a
2343 sequence of (not necessarily constant) expressions.
2348 .faraddr DrawCircle, DrawRectangle, DrawHexagon
2351 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
2354 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
2356 This directive may be used to enable one or more compatibility features
2357 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
2358 possible, it may be useful when porting sources written for other
2359 assemblers. There is no way to switch a feature off, once you have
2360 enabled it, so using
2366 will enable the feature until end of assembly is reached.
2368 The following features are available:
2372 <tag><tt>at_in_identifiers</tt><label id="at_in_identifiers"></tag>
2374 Accept the at character (`@') as a valid character in identifiers. The
2375 at character is not allowed to start an identifier, even with this
2378 <tag><tt>c_comments</tt></tag>
2380 Allow C like comments using <tt>/*</tt> and <tt>*/</tt> as left and right
2381 comment terminators. Note that C comments may not be nested. There's also a
2382 pitfall when using C like comments: All statements must be terminated by
2383 "end-of-line". Using C like comments, it is possible to hide the newline,
2384 which results in error messages. See the following non working example:
2387 lda #$00 /* This comment hides the newline
2391 <tag><tt>dollar_in_identifiers</tt><label id="dollar_in_identifiers"></tag>
2393 Accept the dollar sign (`$') as a valid character in identifiers. The
2394 dollar character is not allowed to start an identifier, even with this
2397 <tag><tt>dollar_is_pc</tt></tag>
2399 The dollar sign may be used as an alias for the star (`*'), which
2400 gives the value of the current PC in expressions.
2401 Note: Assignment to the pseudo variable is not allowed.
2403 <tag><tt>labels_without_colons</tt></tag>
2405 Allow labels without a trailing colon. These labels are only accepted,
2406 if they start at the beginning of a line (no leading white space).
2408 <tag><tt>leading_dot_in_identifiers</tt><label id="leading_dot_in_identifiers"></tag>
2410 Accept the dot (`.') as the first character of an identifier. This may be
2411 used for example to create macro names that start with a dot emulating
2412 control directives of other assemblers. Note however, that none of the
2413 reserved keywords built into the assembler, that starts with a dot, may be
2414 overridden. When using this feature, you may also get into trouble if
2415 later versions of the assembler define new keywords starting with a dot.
2417 <tag><tt>loose_char_term</tt></tag>
2419 Accept single quotes as well as double quotes as terminators for char
2422 <tag><tt>loose_string_term</tt></tag>
2424 Accept single quotes as well as double quotes as terminators for string
2427 <tag><tt>missing_char_term</tt></tag>
2429 Accept single quoted character constants where the terminating quote is
2434 <bf/Note:/ This does not work in conjunction with <tt/.FEATURE
2435 loose_string_term/, since in this case the input would be ambiguous.
2437 <tag><tt>org_per_seg</tt><label id="org_per_seg"></tag>
2439 This feature makes relocatable/absolute mode local to the current segment.
2440 Using <tt><ref id=".ORG" name=".ORG"></tt> when <tt/org_per_seg/ is in
2441 effect will only enable absolute mode for the current segment. Dito for
2442 <tt><ref id=".RELOC" name=".RELOC"></tt>.
2444 <tag><tt>pc_assignment</tt></tag>
2446 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
2447 is enabled). Such an assignment is handled identical to the <tt><ref
2448 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
2449 removing the lines with the assignments may also be an option when porting
2450 code written for older assemblers).
2452 <tag><tt>ubiquitous_idents</tt></tag>
2454 Allow the use of instructions names as names for macros and symbols. This
2455 makes it possible to "overload" instructions by defining a macro with the
2456 same name. This does also make it possible to introduce hard to find errors
2457 in your code, so be careful!
2461 It is also possible to specify features on the command line using the
2462 <tt><ref id="option--feature" name="--feature"></tt> command line option.
2463 This is useful when translating sources written for older assemblers, when
2464 you don't want to change the source code.
2466 As an example, to translate sources written for Andre Fachats xa65
2467 assembler, the features
2470 labels_without_colons, pc_assignment, loose_char_term
2473 may be helpful. They do not make ca65 completely compatible, so you may not
2474 be able to translate the sources without changes, even when enabling these
2475 features. However, I have found several sources that translate without
2476 problems when enabling these features on the command line.
2479 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
2481 Insert an option string into the object file. There are two forms of
2482 this command, one specifies the option by a keyword, the second
2483 specifies it as a number. Since usage of the second one needs knowledge
2484 of the internal encoding, its use is not recommended and I will only
2485 describe the first form here.
2487 The command is followed by one of the keywords
2495 a comma and a string. The option is written into the object file
2496 together with the string value. This is currently unidirectional and
2497 there is no way to actually use these options once they are in the
2503 .fileopt comment, "Code stolen from my brother"
2504 .fileopt compiler, "BASIC 2.0"
2505 .fopt author, "J. R. User"
2509 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
2511 Import an absolute symbol from another module. The command is followed by a
2512 comma separated list of symbols to import. The command is similar to <tt>
2513 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
2514 written to the generated object file, even if the symbol is never referenced
2515 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
2516 references for unused symbols).
2521 .forceimport needthisone, needthistoo
2524 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2527 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
2529 Declare symbols as global. Must be followed by a comma separated list of
2530 symbols to declare. Symbols from the list, that are defined somewhere in the
2531 source, are exported, all others are imported. Additional <tt><ref
2532 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
2533 name=".EXPORT"></tt> commands for the same symbol are allowed.
2542 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
2544 Declare symbols as global. Must be followed by a comma separated list of
2545 symbols to declare. Symbols from the list, that are defined somewhere in the
2546 source, are exported, all others are imported. Additional <tt><ref
2547 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
2548 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
2549 in the list are explicitly marked as zero page symbols.
2557 <sect1><tt>.HIBYTES</tt><label id=".HIBYTES"><p>
2559 Define byte sized data by extracting only the high byte (that is, bits 8-15) from
2560 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
2561 the operator '>' prepended to each expression in its list.
2566 .lobytes $1234, $2345, $3456, $4567
2567 .hibytes $fedc, $edcb, $dcba, $cba9
2570 which is equivalent to
2573 .byte $34, $45, $56, $67
2574 .byte $fe, $ed, $dc, $cb
2580 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
2582 TableLookupLo: .lobytes MyTable
2583 TableLookupHi: .hibytes MyTable
2586 which is equivalent to
2589 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
2590 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
2593 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
2594 <tt><ref id=".LOBYTES" name=".LOBYTES"></tt>,
2595 <tt><ref id=".BANKBYTES" name=".BANKBYTES"></tt>
2598 <sect1><tt>.I16</tt><label id=".I16"><p>
2600 Valid only in 65816 mode. Switch the index registers to 16 bit.
2602 Note: This command will not emit any code, it will tell the assembler to
2603 create 16 bit operands for immediate operands.
2605 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
2606 name=".SMART"></tt> commands.
2609 <sect1><tt>.I8</tt><label id=".I8"><p>
2611 Valid only in 65816 mode. Switch the index registers to 8 bit.
2613 Note: This command will not emit any code, it will tell the assembler to
2614 create 8 bit operands for immediate operands.
2616 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
2617 name=".SMART"></tt> commands.
2620 <sect1><tt>.IF</tt><label id=".IF"><p>
2622 Conditional assembly: Evaluate an expression and switch assembler output
2623 on or off depending on the expression. The expression must be a constant
2624 expression, that is, all operands must be defined.
2626 A expression value of zero evaluates to FALSE, any other value evaluates
2630 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
2632 Conditional assembly: Check if there are any remaining tokens in this line,
2633 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
2634 condition is not true, further lines are not assembled until an <tt><ref
2635 id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2636 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2638 This command is often used to check if a macro parameter was given. Since an
2639 empty macro parameter will evaluate to nothing, the condition will evaluate
2640 to FALSE if an empty parameter was given.
2654 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2657 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
2659 Conditional assembly: Evaluate an expression and switch assembler output
2660 on or off depending on the constness of the expression.
2662 A const expression evaluates to to TRUE, a non const expression (one
2663 containing an imported or currently undefined symbol) evaluates to
2666 See also: <tt><ref id=".CONST" name=".CONST"></tt>
2669 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
2671 Conditional assembly: Check if a symbol is defined. Must be followed by
2672 a symbol name. The condition is true if the the given symbol is already
2673 defined, and false otherwise.
2675 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2678 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
2680 Conditional assembly: Check if there are any remaining tokens in this line,
2681 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
2682 condition is not true, further lines are not assembled until an <tt><ref
2683 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2684 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2686 This command is often used to check if a macro parameter was given.
2687 Since an empty macro parameter will evaluate to nothing, the condition
2688 will evaluate to FALSE if an empty parameter was given.
2701 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2704 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
2706 Conditional assembly: Check if a symbol is defined. Must be followed by
2707 a symbol name. The condition is true if the the given symbol is not
2708 defined, and false otherwise.
2710 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2713 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
2715 Conditional assembly: Check if a symbol is referenced. Must be followed
2716 by a symbol name. The condition is true if if the the given symbol was
2717 not referenced before, and false otherwise.
2719 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2722 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
2724 Conditional assembly: Check if the assembler is currently in 6502 mode
2725 (see <tt><ref id=".P02" name=".P02"></tt> command).
2728 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
2730 Conditional assembly: Check if the assembler is currently in 65816 mode
2731 (see <tt><ref id=".P816" name=".P816"></tt> command).
2734 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
2736 Conditional assembly: Check if the assembler is currently in 65C02 mode
2737 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
2740 <sect1><tt>.IFPSC02</tt><label id=".IFPSC02"><p>
2742 Conditional assembly: Check if the assembler is currently in 65SC02 mode
2743 (see <tt><ref id=".PSC02" name=".PSC02"></tt> command).
2746 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
2748 Conditional assembly: Check if a symbol is referenced. Must be followed
2749 by a symbol name. The condition is true if if the the given symbol was
2750 referenced before, and false otherwise.
2752 This command may be used to build subroutine libraries in include files
2753 (you may use separate object modules for this purpose too).
2758 .ifref ToHex ; If someone used this subroutine
2759 ToHex: tay ; Define subroutine
2765 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2768 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
2770 Import a symbol from another module. The command is followed by a comma
2771 separated list of symbols to import, with each one optionally followed by
2772 an address specification.
2778 .import bar: zeropage
2781 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
2784 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
2786 Import a symbol from another module. The command is followed by a comma
2787 separated list of symbols to import. The symbols are explicitly imported
2788 as zero page symbols (that is, symbols with values in byte range).
2796 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2799 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
2801 Include a file as binary data. The command expects a string argument
2802 that is the name of a file to include literally in the current segment.
2803 In addition to that, a start offset and a size value may be specified,
2804 separated by commas. If no size is specified, all of the file from the
2805 start offset to end-of-file is used. If no start position is specified
2806 either, zero is assumed (which means that the whole file is inserted).
2811 ; Include whole file
2812 .incbin "sprites.dat"
2814 ; Include file starting at offset 256
2815 .incbin "music.dat", $100
2817 ; Read 100 bytes starting at offset 200
2818 .incbin "graphics.dat", 200, 100
2822 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
2824 Include another file. Include files may be nested up to a depth of 16.
2833 <sect1><tt>.INTERRUPTOR</tt><label id=".INTERRUPTOR"><p>
2835 Export a symbol and mark it as an interruptor. This may be used together
2836 with the linker to build a table of interruptor subroutines that are called
2839 Note: The linker has a feature to build a table of marked routines, but it
2840 is your code that must call these routines, so just declaring a symbol as
2841 interruptor does nothing by itself.
2843 An interruptor is always exported as an absolute (16 bit) symbol. You don't
2844 need to use an additional <tt/.export/ statement, this is implied by
2845 <tt/.interruptor/. It may have an optional priority that is separated by a
2846 comma. Higher numeric values mean a higher priority. If no priority is
2847 given, the default priority of 7 is used. Be careful when assigning
2848 priorities to your own module constructors so they won't interfere with the
2849 ones in the cc65 library.
2854 .interruptor IrqHandler
2855 .interruptor Handler, 16
2858 See the <tt><ref id=".CONDES" name=".CONDES"></tt> command and the separate
2859 section <ref id="condes" name="Module constructors/destructors"> explaining
2860 the feature in more detail.
2863 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
2865 Switch on or off line continuations using the backslash character
2866 before a newline. The option is off by default.
2867 Note: Line continuations do not work in a comment. A backslash at the
2868 end of a comment is treated as part of the comment and does not trigger
2870 The command must be followed by a '+' or '-' character to switch the
2871 option on or off respectively.
2876 .linecont + ; Allow line continuations
2879 #$20 ; This is legal now
2883 <sect1><tt>.LIST</tt><label id=".LIST"><p>
2885 Enable output to the listing. The command must be followed by a boolean
2886 switch ("on", "off", "+" or "-") and will enable or disable listing
2888 The option has no effect if the listing is not enabled by the command line
2889 switch -l. If -l is used, an internal counter is set to 1. Lines are output
2890 to the listing file, if the counter is greater than zero, and suppressed if
2891 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
2897 .list on ; Enable listing output
2901 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
2903 Set, how many bytes are shown in the listing for one source line. The
2904 default is 12, so the listing will show only the first 12 bytes for any
2905 source line that generates more than 12 bytes of code or data.
2906 The directive needs an argument, which is either "unlimited", or an
2907 integer constant in the range 4..255.
2912 .listbytes unlimited ; List all bytes
2913 .listbytes 12 ; List the first 12 bytes
2914 .incbin "data.bin" ; Include large binary file
2918 <sect1><tt>.LOBYTES</tt><label id=".LOBYTES"><p>
2920 Define byte sized data by extracting only the low byte (that is, bits 0-7) from
2921 each expression. This is equivalent to <tt><ref id=".BYTE" name=".BYTE"></tt> with
2922 the operator '<' prepended to each expression in its list.
2927 .lobytes $1234, $2345, $3456, $4567
2928 .hibytes $fedc, $edcb, $dcba, $cba9
2931 which is equivalent to
2934 .byte $34, $45, $56, $67
2935 .byte $fe, $ed, $dc, $cb
2941 .define MyTable TableItem0, TableItem1, TableItem2, TableItem3
2943 TableLookupLo: .lobytes MyTable
2944 TableLookupHi: .hibytes MyTable
2947 which is equivalent to
2950 TableLookupLo: .byte <TableItem0, <TableItem1, <TableItem2, <TableItem3
2951 TableLookupHi: .byte >TableItem0, >TableItem1, >TableItem2, >TableItem3
2954 See also: <tt><ref id=".BYTE" name=".BYTE"></tt>,
2955 <tt><ref id=".HIBYTES" name=".HIBYTES"></tt>,
2956 <tt><ref id=".BANKBYTES" name=".BANKBYTES"></tt>
2959 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
2961 This command may only be used inside a macro definition. It declares a
2962 list of identifiers as local to the macro expansion.
2964 A problem when using macros are labels: Since they don't change their name,
2965 you get a "duplicate symbol" error if the macro is expanded the second time.
2966 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
2967 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
2970 Some other assemblers start a new lexical block inside a macro expansion.
2971 This has some drawbacks however, since that will not allow <em/any/ symbol
2972 to be visible outside a macro, a feature that is sometimes useful. The
2973 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
2974 to address the problem.
2976 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
2980 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
2982 Defines the character that start "cheap" local labels. You may use one
2983 of '@' and '?' as start character. The default is '@'.
2985 Cheap local labels are labels that are visible only between two non
2986 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
2987 using explicit lexical nesting.
2994 Clear: lda #$00 ; Global label
2995 ?Loop: sta Mem,y ; Local label
2999 Sub: ... ; New global label
3000 bne ?Loop ; ERROR: Unknown identifier!
3004 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
3006 Insert a predefined macro package. The command is followed by an
3007 identifier specifying the macro package to insert. Available macro
3011 atari Defines the scrcode macro.
3012 cbm Defines the scrcode macro.
3013 cpu Defines constants for the .CPU variable.
3014 generic Defines generic macros like add and sub.
3015 longbranch Defines conditional long jump macros.
3018 Including a macro package twice, or including a macro package that
3019 redefines already existing macros will lead to an error.
3024 .macpack longbranch ; Include macro package
3026 cmp #$20 ; Set condition codes
3027 jne Label ; Jump long on condition
3030 Macro packages are explained in more detail in section <ref
3031 id="macropackages" name="Macro packages">.
3034 <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"><p>
3036 Start a classic macro definition. The command is followed by an identifier
3037 (the macro name) and optionally by a comma separated list of identifiers
3038 that are macro parameters.
3040 See section <ref id="macros" name="Macros">.
3043 <sect1><tt>.ORG</tt><label id=".ORG"><p>
3045 Start a section of absolute code. The command is followed by a constant
3046 expression that gives the new PC counter location for which the code is
3047 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
3050 By default, absolute/relocatable mode is global (valid even when switching
3051 segments). Using <tt>.FEATURE <ref id="org_per_seg" name="org_per_seg"></tt>
3052 it can be made segment local.
3054 Please note that you <em/do not need/ <tt/.ORG/ in most cases. Placing
3055 code at a specific address is the job of the linker, not the assembler, so
3056 there is usually no reason to assemble code to a specific address.
3061 .org $7FF ; Emit code starting at $7FF
3065 <sect1><tt>.OUT</tt><label id=".OUT"><p>
3067 Output a string to the console without producing an error. This command
3068 is similar to <tt/.ERROR/, however, it does not force an assembler error
3069 that prevents the creation of an object file.
3074 .out "This code was written by the codebuster(tm)"
3077 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
3078 id=".ERROR" name=".ERROR"></tt> directives.
3081 <sect1><tt>.P02</tt><label id=".P02"><p>
3083 Enable the 6502 instruction set, disable 65SC02, 65C02 and 65816
3084 instructions. This is the default if not overridden by the
3085 <tt><ref id="option--cpu" name="--cpu"></tt> command line option.
3087 See: <tt><ref id=".PC02" name=".PC02"></tt>, <tt><ref id=".PSC02"
3088 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
3091 <sect1><tt>.P816</tt><label id=".P816"><p>
3093 Enable the 65816 instruction set. This is a superset of the 65SC02 and
3094 6502 instruction sets.
3096 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3097 name=".PSC02"></tt> and <tt><ref id=".PC02" name=".PC02"></tt>
3100 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
3102 Set the page length for the listing. Must be followed by an integer
3103 constant. The value may be "unlimited", or in the range 32 to 127. The
3104 statement has no effect if no listing is generated. The default value is -1
3105 (unlimited) but may be overridden by the <tt/--pagelength/ command line
3106 option. Beware: Since ca65 is a one pass assembler, the listing is generated
3107 after assembly is complete, you cannot use multiple line lengths with one
3108 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
3113 .pagelength 66 ; Use 66 lines per listing page
3115 .pagelength unlimited ; Unlimited page length
3119 <sect1><tt>.PC02</tt><label id=".PC02"><p>
3121 Enable the 65C02 instructions set. This instruction set includes all
3122 6502 and 65SC02 instructions.
3124 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3125 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
3128 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
3130 Pop the last pushed segment from the stack, and set it.
3132 This command will switch back to the segment that was last pushed onto the
3133 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
3134 command, and remove this entry from the stack.
3136 The assembler will print an error message if the segment stack is empty
3137 when this command is issued.
3139 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
3142 <sect1><tt>.PROC</tt><label id=".PROC"><p>
3144 Start a nested lexical level with the given name and adds a symbol with this
3145 name to the enclosing scope. All new symbols from now on are in the local
3146 lexical level and are accessible from outside only via <ref id="scopesyntax"
3147 name="explicit scope specification">. Symbols defined outside this local
3148 level may be accessed as long as their names are not used for new symbols
3149 inside the level. Symbols names in other lexical levels do not clash, so you
3150 may use the same names for identifiers. The lexical level ends when the
3151 <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read. Lexical levels
3152 may be nested up to a depth of 16 (this is an artificial limit to protect
3153 against errors in the source).
3155 Note: Macro names are always in the global level and in a separate name
3156 space. There is no special reason for this, it's just that I've never
3157 had any need for local macro definitions.
3162 .proc Clear ; Define Clear subroutine, start new level
3164 L1: sta Mem,y ; L1 is local and does not cause a
3165 ; duplicate symbol error if used in other
3168 bne L1 ; Reference local symbol
3170 .endproc ; Leave lexical level
3173 See: <tt/<ref id=".ENDPROC" name=".ENDPROC">/ and <tt/<ref id=".SCOPE"
3177 <sect1><tt>.PSC02</tt><label id=".PSC02"><p>
3179 Enable the 65SC02 instructions set. This instruction set includes all
3182 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PC02"
3183 name=".PC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
3186 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
3188 Push the currently active segment onto a stack. The entries on the stack
3189 include the name of the segment and the segment type. The stack has a size
3192 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
3193 to switch to another segment and to restore the old segment later, without
3194 even knowing the name and type of the current segment.
3196 The assembler will print an error message if the segment stack is already
3197 full, when this command is issued.
3199 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
3202 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
3204 Switch back to relocatable mode. See the <tt><ref id=".ORG"
3205 name=".ORG"></tt> command.
3208 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
3210 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
3211 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
3212 a constant expression that tells how many times the commands in the body
3213 should get repeated. Optionally, a comma and an identifier may be specified.
3214 If this identifier is found in the body of the repeat statement, it is
3215 replaced by the current repeat count (starting with zero for the first time
3216 the body is repeated).
3218 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
3219 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
3220 level will be used, not the one from the outer level.
3224 The following macro will emit a string that is "encrypted" in that all
3225 characters of the string are XORed by the value $55.
3229 .repeat .strlen(Arg), I
3230 .byte .strat(Arg, I) ^ $55
3235 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
3238 <sect1><tt>.RES</tt><label id=".RES"><p>
3240 Reserve storage. The command is followed by one or two constant
3241 expressions. The first one is mandatory and defines, how many bytes of
3242 storage should be defined. The second, optional expression must by a
3243 constant byte value that will be used as value of the data. If there
3244 is no fill value given, the linker will use the value defined in the
3245 linker configuration file (default: zero).
3250 ; Reserve 12 bytes of memory with value $AA
3255 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
3257 Switch to the RODATA segment. The name of the RODATA segment is always
3258 "RODATA", so this is a shortcut for
3264 The RODATA segment is a segment that is used by the compiler for
3265 readonly data like string constants.
3267 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
3270 <sect1><tt>.SCOPE</tt><label id=".SCOPE"><p>
3272 Start a nested lexical level with the given name. All new symbols from now
3273 on are in the local lexical level and are accessible from outside only via
3274 <ref id="scopesyntax" name="explicit scope specification">. Symbols defined
3275 outside this local level may be accessed as long as their names are not used
3276 for new symbols inside the level. Symbols names in other lexical levels do
3277 not clash, so you may use the same names for identifiers. The lexical level
3278 ends when the <tt><ref id=".ENDSCOPE" name=".ENDSCOPE"></tt> command is
3279 read. Lexical levels may be nested up to a depth of 16 (this is an
3280 artificial limit to protect against errors in the source).
3282 Note: Macro names are always in the global level and in a separate name
3283 space. There is no special reason for this, it's just that I've never
3284 had any need for local macro definitions.
3289 .scope Error ; Start new scope named Error
3291 File = 1 ; File error
3292 Parse = 2 ; Parse error
3293 .endscope ; Close lexical level
3296 lda #Error::File ; Use symbol from scope Error
3299 See: <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/ and <tt/<ref id=".PROC"
3303 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
3305 Switch to another segment. Code and data is always emitted into a
3306 segment, that is, a named section of data. The default segment is
3307 "CODE". There may be up to 254 different segments per object file
3308 (and up to 65534 per executable). There are shortcut commands for
3309 the most common segments ("CODE", "DATA" and "BSS").
3311 The command is followed by a string containing the segment name (there are
3312 some constraints for the name - as a rule of thumb use only those segment
3313 names that would also be valid identifiers). There may also be an optional
3314 address size separated by a colon. See the section covering <tt/<ref
3315 id="address-sizes" name="address sizes">/ for more information.
3317 The default address size for a segment depends on the memory model specified
3318 on the command line. The default is "absolute", which means that you don't
3319 have to use an address size modifier in most cases.
3321 "absolute" means that the is a segment with 16 bit (absolute) addressing.
3322 That is, the segment will reside somewhere in core memory outside the zero
3323 page. "zeropage" (8 bit) means that the segment will be placed in the zero
3324 page and direct (short) addressing is possible for data in this segment.
3326 Beware: Only labels in a segment with the zeropage attribute are marked
3327 as reachable by short addressing. The `*' (PC counter) operator will
3328 work as in other segments and will create absolute variable values.
3330 Please note that a segment cannot have two different address sizes. A
3331 segment specified as zeropage cannot be declared as being absolute later.
3336 .segment "ROM2" ; Switch to ROM2 segment
3337 .segment "ZP2": zeropage ; New direct segment
3338 .segment "ZP2" ; Ok, will use last attribute
3339 .segment "ZP2": absolute ; Error, redecl mismatch
3342 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
3343 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref
3344 id=".RODATA" name=".RODATA"></tt>
3347 <sect1><tt>.SETCPU</tt><label id=".SETCPU"><p>
3349 Switch the CPU instruction set. The command is followed by a string that
3350 specifies the CPU. Possible values are those that can also be supplied to
3351 the <tt><ref id="option--cpu" name="--cpu"></tt> command line option,
3352 namely: 6502, 6502X, 65SC02, 65C02, 65816, sunplus and HuC6280. Please
3353 note that support for the sunplus CPU is not available in the freeware
3354 version, because the instruction set of the sunplus CPU is "proprietary
3357 See: <tt><ref id=".CPU" name=".CPU"></tt>,
3358 <tt><ref id=".IFP02" name=".IFP02"></tt>,
3359 <tt><ref id=".IFP816" name=".IFP816"></tt>,
3360 <tt><ref id=".IFPC02" name=".IFPC02"></tt>,
3361 <tt><ref id=".IFPSC02" name=".IFPSC02"></tt>,
3362 <tt><ref id=".P02" name=".P02"></tt>,
3363 <tt><ref id=".P816" name=".P816"></tt>,
3364 <tt><ref id=".PC02" name=".PC02"></tt>,
3365 <tt><ref id=".PSC02" name=".PSC02"></tt>
3368 <sect1><tt>.SMART</tt><label id=".SMART"><p>
3370 Switch on or off smart mode. The command must be followed by a '+' or '-'
3371 character to switch the option on or off respectively. The default is off
3372 (that is, the assembler doesn't try to be smart), but this default may be
3373 changed by the -s switch on the command line.
3375 In smart mode the assembler will do the following:
3378 <item>Track usage of the <tt/REP/ and <tt/SEP/ instructions in 65816 mode
3379 and update the operand sizes accordingly. If the operand of such an
3380 instruction cannot be evaluated by the assembler (for example, because
3381 the operand is an imported symbol), a warning is issued. Beware: Since
3382 the assembler cannot trace the execution flow this may lead to false
3383 results in some cases. If in doubt, use the <tt/.Inn/ and <tt/.Ann/
3384 instructions to tell the assembler about the current settings.
3385 <item>In 65816 mode, replace a <tt/RTS/ instruction by <tt/RTL/ if it is
3386 used within a procedure declared as <tt/far/, or if the procedure has
3387 no explicit address specification, but it is <tt/far/ because of the
3395 .smart - ; Stop being smart
3398 See: <tt><ref id=".A16" name=".A16"></tt>,
3399 <tt><ref id=".A8" name=".A8"></tt>,
3400 <tt><ref id=".I16" name=".I16"></tt>,
3401 <tt><ref id=".I8" name=".I8"></tt>
3404 <sect1><tt>.STRUCT</tt><label id=".STRUCT"><p>
3406 Starts a struct definition. Structs are covered in a separate section named
3407 <ref id="structs" name=""Structs and unions"">.
3409 See: <tt><ref id=".ENDSTRUCT" name=".ENDSTRUCT"></tt>
3412 <sect1><tt>.SUNPLUS</tt><label id=".SUNPLUS"><p>
3414 Enable the SunPlus instructions set. This command will not work in the
3415 freeware version of the assembler, because the instruction set is
3416 "proprietary and confidential".
3418 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3419 name=".PSC02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt>, and
3420 <tt><ref id=".P816" name=".P816"></tt>
3423 <sect1><tt>.TAG</tt><label id=".TAG"><p>
3425 Allocate space for a struct or union.
3436 .tag Point ; Allocate 4 bytes
3440 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
3442 Force an assembly warning. The assembler will output a warning message
3443 preceded by "User warning". This warning will always be output, even if
3444 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
3445 command line option.
3447 This command may be used to output possible problems when assembling
3456 .warning "Forward jump in jne, cannot optimize!"
3466 See also the <tt><ref id=".ERROR" name=".ERROR"></tt> and <tt><ref id=".OUT"
3467 name=".OUT"></tt> directives.
3470 <sect1><tt>.WORD</tt><label id=".WORD"><p>
3472 Define word sized data. Must be followed by a sequence of (word ranged,
3473 but not necessarily constant) expressions.
3478 .word $0D00, $AF13, _Clear
3482 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
3484 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
3485 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
3489 .segment "ZEROPAGE", zeropage
3492 Because of the "zeropage" attribute, labels declared in this segment are
3493 addressed using direct addressing mode if possible. You <em/must/ instruct
3494 the linker to place this segment somewhere in the address range 0..$FF
3495 otherwise you will get errors.
3497 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
3501 <sect>Macros<label id="macros"><p>
3504 <sect1>Introduction<p>
3506 Macros may be thought of as "parametrized super instructions". Macros are
3507 sequences of tokens that have a name. If that name is used in the source
3508 file, the macro is "expanded", that is, it is replaced by the tokens that
3509 were specified when the macro was defined.
3512 <sect1>Macros without parameters<p>
3514 In it's simplest form, a macro does not have parameters. Here's an
3518 .macro asr ; Arithmetic shift right
3519 cmp #$80 ; Put bit 7 into carry
3520 ror ; Rotate right with carry
3524 The macro above consists of two real instructions, that are inserted into
3525 the code, whenever the macro is expanded. Macro expansion is simply done
3526 by using the name, like this:
3535 <sect1>Parametrized macros<p>
3537 When using macro parameters, macros can be even more useful:
3551 When calling the macro, you may give a parameter, and each occurrence of
3552 the name "addr" in the macro definition will be replaced by the given
3571 A macro may have more than one parameter, in this case, the parameters
3572 are separated by commas. You are free to give less parameters than the
3573 macro actually takes in the definition. You may also leave intermediate
3574 parameters empty. Empty parameters are replaced by empty space (that is,
3575 they are removed when the macro is expanded). If you have a look at our
3576 macro definition above, you will see, that replacing the "addr" parameter
3577 by nothing will lead to wrong code in most lines. To help you, writing
3578 macros with a variable parameter list, there are some control commands:
3580 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
3581 returns true, if there are any tokens on the remainder of the line. Since
3582 empty parameters are replaced by nothing, this may be used to test if a given
3583 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
3586 Look at this example:
3589 .macro ldaxy a, x, y
3602 This macro may be called as follows:
3605 ldaxy 1, 2, 3 ; Load all three registers
3607 ldaxy 1, , 3 ; Load only a and y
3609 ldaxy , , 3 ; Load y only
3612 There's another helper command for determining, which macro parameters are
3613 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is
3614 replaced by the parameter count given, <em/including/ intermediate empty macro
3618 ldaxy 1 ; .PARAMCOUNT = 1
3619 ldaxy 1,,3 ; .PARAMCOUNT = 3
3620 ldaxy 1,2 ; .PARAMCOUNT = 2
3621 ldaxy 1, ; .PARAMCOUNT = 2
3622 ldaxy 1,2,3 ; .PARAMCOUNT = 3
3625 Macro parameters may optionally be enclosed into curly braces. This allows the
3626 inclusion of tokens that would otherwise terminate the parameter (the comma in
3627 case of a macro parameter).
3630 .macro foo arg1, arg2
3634 foo ($00,x) ; Two parameters passed
3635 foo {($00,x)} ; One parameter passed
3638 In the first case, the macro is called with two parameters: '<tt/($00/'
3639 and 'x)'. The comma is not passed to the macro, since it is part of the
3640 calling sequence, not the parameters.
3642 In the second case, '($00,x)' is passed to the macro, this time
3643 including the comma.
3646 <sect1>Detecting parameter types<p>
3648 Sometimes it is nice to write a macro that acts differently depending on the
3649 type of the argument supplied. An example would be a macro that loads a 16 bit
3650 value from either an immediate operand, or from memory. The <tt/<ref
3651 id=".MATCH" name=".MATCH">/ and <tt/<ref id=".XMATCH" name=".XMATCH">/
3652 functions will allow you to do exactly this:
3656 .if (.match (.left (1, {arg}), #))
3658 lda #<(.right (.tcount ({arg})-1, {arg}))
3659 ldx #>(.right (.tcount ({arg})-1, {arg}))
3661 ; assume absolute or zero page
3668 Using the <tt/<ref id=".MATCH" name=".MATCH">/ function, the macro is able to
3669 check if its argument begins with a hash mark. If so, two immediate loads are
3670 emitted, Otherwise a load from an absolute zero page memory location is
3671 assumed. Please note how the curly braces are used to enclose parameters to
3672 pseudo functions handling token lists. This is necessary, because the token
3673 lists may include commas or parens, which would be treated by the assembler
3676 The macro can be used as
3681 ldax #$1234 ; X=$12, A=$34
3683 ldax foo ; X=$56, A=$78
3687 <sect1>Recursive macros<p>
3689 Macros may be used recursively:
3692 .macro push r1, r2, r3
3701 There's also a special macro to help writing recursive macros: <tt><ref
3702 id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion
3706 .macro push r1, r2, r3, r4, r5, r6, r7
3708 ; First parameter is empty
3714 push r2, r3, r4, r5, r6, r7
3718 When expanding this macro, the expansion will push all given parameters
3719 until an empty one is encountered. The macro may be called like this:
3722 push $20, $21, $32 ; Push 3 ZP locations
3723 push $21 ; Push one ZP location
3727 <sect1>Local symbols inside macros<p>
3729 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
3730 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
3731 Have a look at the inc16 macro above. Here is it again:
3745 If you have a closer look at the code, you will notice, that it could be
3746 written more efficiently, like this:
3757 But imagine what happens, if you use this macro twice? Since the label
3758 "Skip" has the same name both times, you get a "duplicate symbol" error.
3759 Without a way to circumvent this problem, macros are not as useful, as
3760 they could be. One solution is, to start a new lexical block inside the
3774 Now the label is local to the block and not visible outside. However,
3775 sometimes you want a label inside the macro to be visible outside. To make
3776 that possible, there's a new command that's only usable inside a macro
3777 definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one
3778 or more symbols as local to the macro expansion. The names of local variables
3779 are replaced by a unique name in each separate macro expansion. So we could
3780 also solve the problem above by using <tt/.LOCAL/:
3784 .local Skip ; Make Skip a local symbol
3791 Skip: ; Not visible outside
3796 <sect1>C style macros<p>
3798 Starting with version 2.5 of the assembler, there is a second macro type
3799 available: C style macros using the <tt/.DEFINE/ directive. These macros are
3800 similar to the classic macro type described above, but behaviour is sometimes
3805 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
3806 span more than a line. You may use line continuation (see <tt><ref
3807 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
3808 more than one line for increased readability, but the macro itself
3809 may not contain an end-of-line token.
3811 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
3812 the name space with classic macros, but they are detected and replaced
3813 at the scanner level. While classic macros may be used in every place,
3814 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
3815 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
3816 they are more versatile in some situations.
3818 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
3819 parameters. While classic macros may have empty parameters, this is
3820 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
3821 For this macro type, the number of actual parameters must match
3822 exactly the number of formal parameters.
3824 To make this possible, formal parameters are enclosed in braces when
3825 defining the macro. If there are no parameters, the empty braces may
3828 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
3829 contain end-of-line tokens, there are things that cannot be done. They
3830 may not contain several processor instructions for example. So, while
3831 some things may be done with both macro types, each type has special
3832 usages. The types complement each other.
3836 Let's look at a few examples to make the advantages and disadvantages
3839 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
3840 following <tt/.DEFINE/:
3845 foo EQU $1234 ; This is accepted now
3848 You may use the directive to define string constants used elsewhere:
3851 ; Define the version number
3852 .define VERSION "12.3a"
3858 Macros with parameters may also be useful:
3861 .define DEBUG(message) .out message
3863 DEBUG "Assembling include file #3"
3866 Note that, while formal parameters have to be placed in braces, this is
3867 not true for the actual parameters. Beware: Since the assembler cannot
3868 detect the end of one parameter, only the first token is used. If you
3869 don't like that, use classic macros instead:
3877 (This is an example where a problem can be solved with both macro types).
3880 <sect1>Characters in macros<p>
3882 When using the <ref id="option-t" name="-t"> option, characters are translated
3883 into the target character set of the specific machine. However, this happens
3884 as late as possible. This means that strings are translated if they are part
3885 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
3886 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
3887 used as part of an expression.
3889 This behaviour is very intuitive outside of macros but may be confusing when
3890 doing more complex macros. If you compare characters against numeric values,
3891 be sure to take the translation into account.
3896 <sect>Macro packages<label id="macropackages"><p>
3898 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
3899 macro packages may be included with just one command. Available macro packages
3903 <sect1><tt>.MACPACK generic</tt><p>
3905 This macro package defines macros that are useful in almost any program.
3906 Currently, two macros are defined:
3921 <sect1><tt>.MACPACK longbranch</tt><p>
3923 This macro package defines long conditional jumps. They are named like the
3924 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
3925 definition for the "<tt/jeq/" macro, the other macros are built using the same
3930 .if .def(Target) .and ((*+2)-(Target) <= 127)
3939 All macros expand to a short branch, if the label is already defined (back
3940 jump) and is reachable with a short jump. Otherwise the macro expands to a
3941 conditional branch with the branch condition inverted, followed by an absolute
3942 jump to the actual branch target.
3944 The package defines the following macros:
3947 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
3952 <sect1><tt>.MACPACK cbm</tt><p>
3954 The cbm macro package will define a macro named <tt/scrcode/. It takes a
3955 string as argument and places this string into memory translated into screen
3959 <sect1><tt>.MACPACK cpu</tt><p>
3961 This macro package does not define any macros but constants used to examine
3962 the value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable. For
3963 each supported CPU a constant similar to
3975 is defined. These constants may be used to determine the exact type of the
3976 currently enabled CPU. In addition to that, for each CPU instruction set,
3977 another constant is defined:
3989 The value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable may
3990 be checked with <tt/<ref id="operators" name=".BITAND">/ to determine if the
3991 currently enabled CPU supports a specific instruction set. For example the
3992 65C02 supports all instructions of the 65SC02 CPU, so it has the
3993 <tt/CPU_ISET_65SC02/ bit set in addition to its native <tt/CPU_ISET_65C02/
3997 .if (.cpu .bitand CPU_ISET_65SC02)
4005 it is possible to determine if the
4011 instruction is supported, which is the case for the 65SC02, 65C02 and 65816
4012 CPUs (the latter two are upwards compatible to the 65SC02).
4016 <sect>Predefined constants<label id="predefined-constants"><p>
4018 For better orthogonality, the assembler defines similar symbols as the
4019 compiler, depending on the target system selected:
4022 <item><tt/__APPLE2__/ - Target system is <tt/apple2/
4023 <item><tt/__APPLE2ENH__/ - Target system is <tt/apple2enh/
4024 <item><tt/__ATARI__/ - Target system is <tt/atari/
4025 <item><tt/__ATMOS__/ - Target system is <tt/atmos/
4026 <item><tt/__BBC__/ - Target system is <tt/bbc/
4027 <item><tt/__C128__/ - Target system is <tt/c128/
4028 <item><tt/__C16__/ - Target system is <tt/c16/
4029 <item><tt/__C64__/ - Target system is <tt/c64/
4030 <item><tt/__CBM__/ - Target is a Commodore system
4031 <item><tt/__CBM510__/ - Target system is <tt/cbm510/
4032 <item><tt/__CBM610__/ - Target system is <tt/cbm610/
4033 <item><tt/__GEOS__/ - Target system is <tt/geos/
4034 <item><tt/__LUNIX__/ - Target system is <tt/lunix/
4035 <item><tt/__NES__/ - Target system is <tt/nes/
4036 <item><tt/__PET__/ - Target system is <tt/pet/
4037 <item><tt/__PLUS4__/ - Target system is <tt/plus4/
4038 <item><tt/__SUPERVISION__/ - Target system is <tt/supervision/
4039 <item><tt/__VIC20__/ - Target system is <tt/vic20/
4043 <sect>Structs and unions<label id="structs"><p>
4045 <sect1>Structs and unions Overview<p>
4047 Structs and unions are special forms of <ref id="scopes" name="scopes">. They
4048 are to some degree comparable to their C counterparts. Both have a list of
4049 members. Each member allocates storage and may optionally have a name, which,
4050 in case of a struct, is the offset from the beginning and, in case of a union,
4054 <sect1>Declaration<p>
4056 Here is an example for a very simple struct with two members and a total size
4066 A union shares the total space between all its members, its size is the same
4067 as that of the largest member.
4069 A struct or union must not necessarily have a name. If it is anonymous, no
4070 local scope is opened, the identifiers used to name the members are placed
4071 into the current scope instead.
4073 A struct may contain unnamed members and definitions of local structs. The
4074 storage allocators may contain a multiplier, as in the example below:
4079 .word 2 ; Allocate two words
4086 <sect1>The <tt/.TAG/ keyword<p>
4088 Using the <ref id=".TAG" name=".TAG"> keyword, it is possible to reserve space
4089 for an already defined struct or unions within another struct:
4103 Space for a struct or union may be allocated using the <ref id=".TAG"
4104 name=".TAG"> directive.
4110 Currently, members are just offsets from the start of the struct or union. To
4111 access a field of a struct, the member offset has to be added to the address
4112 of the struct itself:
4115 lda C+Circle::Radius ; Load circle radius into A
4118 This may change in a future version of the assembler.
4121 <sect1>Limitations<p>
4123 Structs and unions are currently implemented as nested symbol tables (in fact,
4124 they were a by-product of the improved scoping rules). Currently, the
4125 assembler has no idea of types. This means that the <ref id=".TAG"
4126 name=".TAG"> keyword will only allocate space. You won't be able to initialize
4127 variables declared with <ref id=".TAG" name=".TAG">, and adding an embedded
4128 structure to another structure with <ref id=".TAG" name=".TAG"> will not make
4129 this structure accessible by using the '::' operator.
4133 <sect>Module constructors/destructors<label id="condes"><p>
4135 <em>Note:</em> This section applies mostly to C programs, so the explanation
4136 below uses examples from the C libraries. However, the feature may also be
4137 useful for assembler programs.
4140 <sect1>Module constructors/destructors Overview<p>
4142 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
4143 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
4144 name=".INTERRUPTOR"></tt> keywords it it possible to export functions in a
4145 special way. The linker is able to generate tables with all functions of a
4146 specific type. Such a table will <em>only</em> include symbols from object
4147 files that are linked into a specific executable. This may be used to add
4148 initialization and cleanup code for library modules, or a table of interrupt
4151 The C heap functions are an example where module initialization code is used.
4152 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
4153 variables that contain the start and the end of the heap, pointers to the free
4154 list and so on. Since the end of the heap depends on the size and start of the
4155 stack, it must be initialized at runtime. However, initializing these
4156 variables for programs that do not use the heap are a waste of time and
4159 So the central module defines a function that contains initialization code and
4160 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
4161 this module is added to an executable by the linker, the initialization
4162 function will be placed into the table of constructors by the linker. The C
4163 startup code will call all constructors before <tt/main/ and all destructors
4164 after <tt/main/, so without any further work, the heap initialization code is
4165 called once the module is linked in.
4167 While it would be possible to add explicit calls to initialization functions
4168 in the startup code, the new approach has several advantages:
4172 If a module is not included, the initialization code is not linked in and not
4173 called. So you don't pay for things you don't need.
4176 Adding another library that needs initialization does not mean that the
4177 startup code has to be changed. Before we had module constructors and
4178 destructors, the startup code for all systems had to be adjusted to call the
4179 new initialization code.
4182 The feature saves memory: Each additional initialization function needs just
4183 two bytes in the table (a pointer to the function).
4188 <sect1>Calling order<p>
4190 The symbols are sorted in increasing priority order by the linker when using
4191 one of the builtin linker configurations, so the functions with lower
4192 priorities come first and are followed by those with higher priorities. The C
4193 library runtime subroutine that walks over the function tables calls the
4194 functions starting from the top of the table - which means that functions with
4195 a high priority are called first.
4197 So when using the C runtime, functions are called with high priority functions
4198 first, followed by low priority functions.
4203 When using these special symbols, please take care of the following:
4208 The linker will only generate function tables, it will not generate code to
4209 call these functions. If you're using the feature in some other than the
4210 existing C environments, you have to write code to call all functions in a
4211 linker generated table yourself. See the <tt/condes/ and <tt/callirq/ modules
4212 in the C runtime for an example on how to do this.
4215 The linker will only add addresses of functions that are in modules linked to
4216 the executable. This means that you have to be careful where to place the
4217 condes functions. If initialization or an irq handler is needed for a group of
4218 functions, be sure to place the function into a module that is linked in
4219 regardless of which function is called by the user.
4222 The linker will generate the tables only when requested to do so by the
4223 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
4224 be requested separately.
4227 Constructors and destructors may have priorities. These priorities determine
4228 the order of the functions in the table. If your initialization or cleanup code
4229 does depend on other initialization or cleanup code, you have to choose the
4230 priority for the functions accordingly.
4233 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
4234 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
4235 name=".INTERRUPTOR"></tt> statements, there is also a more generic command:
4236 <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to specify an
4237 additional type. Predefined types are 0 (constructor), 1 (destructor) and 2
4238 (interruptor). The linker generates a separate table for each type on request.
4243 <sect>Porting sources from other assemblers<p>
4245 Sometimes it is necessary to port code written for older assemblers to ca65.
4246 In some cases, this can be done without any changes to the source code by
4247 using the emulation features of ca65 (see <tt><ref id=".FEATURE"
4248 name=".FEATURE"></tt>). In other cases, it is necessary to make changes to the
4251 Probably the biggest difference is the handling of the <tt><ref id=".ORG"
4252 name=".ORG"></tt> directive. ca65 generates relocatable code, and placement is
4253 done by the linker. Most other assemblers generate absolute code, placement is
4254 done within the assembler and there is no external linker.
4256 In general it is not a good idea to write new code using the emulation
4257 features of the assembler, but there may be situations where even this rule is
4262 You need to use some of the ca65 emulation features to simulate the behaviour
4263 of such simple assemblers.
4266 <item>Prepare your sourcecode like this:
4269 ; if you want TASS style labels without colons
4270 .feature labels_without_colons
4272 ; if you want TASS style character constants
4273 ; ("a" instead of the default 'a')
4274 .feature loose_char_term
4276 .word *+2 ; the cbm load address
4281 notice that the two emulation features are mostly useful for porting
4282 sources originally written in/for TASS, they are not needed for the
4283 actual "simple assembler operation" and are not recommended if you are
4284 writing new code from scratch.
4286 <item>Replace all program counter assignments (which are not possible in ca65
4287 by default, and the respective emulation feature works different from what
4288 you'd expect) by another way to skip to memory locations, for example the
4289 <tt><ref id=".RES" name=".RES"></tt> directive.
4293 .res $2000-* ; reserve memory up to $2000
4296 Please note that other than the original TASS, ca65 can never move the program
4297 counter backwards - think of it as if you are assembling to disk with TASS.
4299 <item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.goto/ etc.) must be
4300 rewritten to match ca65 syntax. Most importantly notice that due to the lack
4301 of <tt/.goto/, everything involving loops must be replaced by
4302 <tt><ref id=".REPEAT" name=".REPEAT"></tt>.
4304 <item>To assemble code to a different address than it is executed at, use the
4305 <tt><ref id=".ORG" name=".ORG"></tt> directive instead of
4306 <tt/.offs/-constructs.
4313 .reloc ; back to normal
4316 <item>Then assemble like this:
4319 cl65 --start-addr 0x0ffe -t none myprog.s -o myprog.prg
4322 Note that you need to use the actual start address minus two, since two bytes
4323 are used for the cbm load address.
4328 <sect>Bugs/Feedback<p>
4330 If you have problems using the assembler, if you find any bugs, or if
4331 you're doing something interesting with the assembler, I would be glad to
4332 hear from you. Feel free to contact me by email
4333 (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
4339 ca65 (and all cc65 binutils) are (C) Copyright 1998-2003 Ullrich von
4340 Bassewitz. For usage of the binaries and/or sources the following
4341 conditions do apply:
4343 This software is provided 'as-is', without any expressed or implied
4344 warranty. In no event will the authors be held liable for any damages
4345 arising from the use of this software.
4347 Permission is granted to anyone to use this software for any purpose,
4348 including commercial applications, and to alter it and redistribute it
4349 freely, subject to the following restrictions:
4352 <item> The origin of this software must not be misrepresented; you must not
4353 claim that you wrote the original software. If you use this software
4354 in a product, an acknowledgment in the product documentation would be
4355 appreciated but is not required.
4356 <item> Altered source versions must be plainly marked as such, and must not
4357 be misrepresented as being the original software.
4358 <item> This notice may not be removed or altered from any source