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 --cpu type Set cpu type
108 --debug-info Add debug info to object file
109 --feature name Set an emulation feature
110 --help Help (this text)
111 --ignore-case Ignore case of symbols
112 --include-dir dir Set an include directory search path
113 --listing Create a listing if assembly was ok
114 --list-bytes n Maximum number of bytes per listing line
115 --macpack-dir dir Set a macro package directory
116 --memory-model model Set the memory model
117 --pagelength n Set the page length for the listing
118 --smart Enable smart mode
119 --target sys Set the target system
120 --verbose Increase verbosity
121 --version Print the assembler version
122 ---------------------------------------------------------------------------
126 <sect1>Command line options in detail<p>
128 Here is a description of all the command line options:
132 <label id="option--cpu">
133 <tag><tt>--cpu type</tt></tag>
135 Set the default for the CPU type. The option takes a parameter, which
138 6502, 65SC02, 65C02, 65816, sunplus, sweet16, HuC6280
140 The sunplus cpu is not available in the freeware version, because the
141 instruction set is "proprietary and confidential".
144 <label id="option--feature">
145 <tag><tt>--feature name</tt></tag>
147 Enable an emulation feature. This is identical as using <tt/.FEATURE/
148 in the source with two exceptions: Feature names must be lower case, and
149 each feature must be specified by using an extra <tt/--feature/ option,
150 comma separated lists are not allowed.
152 See the discussion of the <tt><ref id=".FEATURE" name=".FEATURE"></tt>
153 command for a list of emulation features.
156 <label id="option-g">
157 <tag><tt>-g, --debug-info</tt></tag>
159 When this option (or the equivalent control command <tt/.DEBUGINFO/) is
160 used, the assembler will add a section to the object file that contains
161 all symbols (including local ones) together with the symbol values and
162 source file positions. The linker will put these additional symbols into
163 the VICE label file, so even local symbols can be seen in the VICE
167 <tag><tt>-h, --help</tt></tag>
169 Print the short option summary shown above.
172 <tag><tt>-i, --ignore-case</tt></tag>
174 This option makes the assembler case insensitive on identifiers and labels.
175 This option will override the default, but may itself be overridden by the
176 <tt><ref id=".CASE" name=".CASE"></tt> control command.
179 <tag><tt>-l, --listing</tt></tag>
181 Generate an assembler listing. The listing file will always have the
182 name of the main input file with the extension replaced by ".lst". This
183 may change in future versions.
186 <tag><tt>--list-bytes n</tt></tag>
188 Set the maximum number of bytes printed in the listing for one line of
189 input. See the <tt><ref id=".LISTBYTES" name=".LISTBYTES"></tt> directive
190 for more information. The value zero can be used to encode an unlimited
191 number of printed bytes.
194 <tag><tt>--macpack-dir dir</tt></tag>
196 This options allows to specify a directory containing macro files that are
197 used instead of the builtin images when a <tt><ref id=".MACPACK"
198 name=".MACPACK"></tt> directive is encountered. If <tt>--macpack-dir</tt>
199 was specified, a <tt>.mac</tt> extension is added to the package name and
200 the resulting file is loaded from the given directory. This is most useful
201 when debugging the builtin macro packages.
204 <tag><tt>-mm model, --memory-model model</tt></tag>
206 Define the default memory model. Possible model specifiers are near, far and
210 <tag><tt>-o name</tt></tag>
212 The default output name is the name of the input file with the extension
213 replaced by ".o". If you don't like that, you may give another name with
214 the -o option. The output file will be placed in the same directory as
215 the source file, or, if -o is given, the full path in this name is used.
218 <tag><tt>--pagelength n</tt></tag>
220 sets the length of a listing page in lines. See the <tt><ref
221 id=".PAGELENGTH" name=".PAGELENGTH"></tt> directive for more information.
224 <tag><tt>-s, --smart-mode</tt></tag>
226 In smart mode (enabled by -s or the <tt><ref id=".SMART" name=".SMART"></tt>
227 pseudo instruction) the assembler will track usage of the <tt/REP/ and
228 <tt/SEP/ instructions in 65816 mode and update the operand sizes
229 accordingly. If the operand of such an instruction cannot be evaluated by
230 the assembler (for example, because the operand is an imported symbol), a
233 Beware: Since the assembler cannot trace the execution flow this may
234 lead to false results in some cases. If in doubt, use the .ixx and .axx
235 instructions to tell the assembler about the current settings. Smart
236 mode is off by default.
239 <label id="option-t">
240 <tag><tt>-t sys, --target sys</tt></tag>
242 Set the target system. This will enable translation of character strings
243 and character constants into the character set of the target platform.
244 The default for the target system is "none", which means that no translation
245 will take place. The assembler supports the same target systems as the
246 compiler, see there for a list.
249 <tag><tt>-v, --verbose</tt></tag>
251 Increase the assembler verbosity. Usually only needed for debugging
252 purposes. You may use this option more than one time for even more
256 <tag><tt>-D</tt></tag>
258 This option allows you to define symbols on the command line. Without a
259 value, the symbol is defined with the value zero. When giving a value,
260 you may use the '$' prefix for hexadecimal symbols. Please note
261 that for some operating systems, '$' has a special meaning, so
262 you may have to quote the expression.
265 <tag><tt>-I dir, --include-dir dir</tt></tag>
267 Name a directory which is searched for include files. The option may be
268 used more than once to specify more than one directory to search. The
269 current directory is always searched first before considering any
270 additional directories.
273 <tag><tt>-U, --auto-import</tt></tag>
275 Mark symbols that are not defined in the sources as imported symbols. This
276 should be used with care since it delays error messages about typos and such
277 until the linker is run. The compiler uses the equivalent of this switch
278 (<tt><ref id=".AUTOIMPORT" name=".AUTOIMPORT"></tt>) to enable auto imported
279 symbols for the runtime library. However, the compiler is supposed to
280 generate code that runs through the assembler without problems, something
281 which is not always true for assembler programmers.
284 <tag><tt>-V, --version</tt></tag>
286 Print the version number of the assembler. If you send any suggestions
287 or bugfixes, please include the version number.
290 <label id="option-W">
291 <tag><tt>-Wn</tt></tag>
293 Set the warning level for the assembler. Using -W2 the assembler will
294 even warn about such things like unused imported symbols. The default
295 warning level is 1, and it would probably be silly to set it to
302 <sect>Input format<p>
304 <sect1>Assembler syntax<p>
306 The assembler accepts the standard 6502/65816 assembler syntax. One line may
307 contain a label (which is identified by a colon), and, in addition to the
308 label, an assembler mnemonic, a macro, or a control command (see section <ref
309 id="control-commands" name="Control Commands"> for supported control
310 commands). Alternatively, the line may contain a symbol definition using
311 the '=' token. Everything after a semicolon is handled as a comment (that is,
314 Here are some examples for valid input lines:
317 Label: ; A label and a comment
318 lda #$20 ; A 6502 instruction plus comment
319 L1: ldx #$20 ; Same with label
320 L2: .byte "Hello world" ; Label plus control command
321 mymac $20 ; Macro expansion
322 MySym = 3*L1 ; Symbol definition
323 MaSym = Label ; Another symbol
326 The assembler accepts
329 <item>all valid 6502 mnemonics when in 6502 mode (the default or after the
330 <tt><ref id=".P02" name=".P02"></tt> command was given).
331 <item>all valid 6502 mnemonics plus a set of illegal instructions when in
332 <ref id="6502X-mode" name="6502X mode">.
333 <item>all valid 65SC02 mnemonics when in 65SC02 mode (after the
334 <tt><ref id=".PSC02" name=".PSC02"></tt> command was given).
335 <item>all valid 65C02 mnemonics when in 65C02 mode (after the
336 <tt><ref id=".PC02" name=".PC02"></tt> command was given).
337 <item>all valid 65618 mnemonics when in 65816 mode (after the
338 <tt><ref id=".P816" name=".P816"></tt> command was given).
339 <item>all valid SunPlus mnemonics when in SunPlus mode (after the
340 <tt><ref id=".SUNPLUS" name=".SUNPLUS"></tt> command was given).
346 In 65816 mode several aliases are accepted in addition to the official
350 BGE is an alias for BCS
351 BLT is an alias for BCC
352 CPA is an alias for CMP
353 DEA is an alias for DEC A
354 INA is an alias for INC A
355 SWA is an alias for XBA
356 TAD is an alias for TCD
357 TAS is an alias for TCS
358 TDA is an alias for TDC
359 TSA is an alias for TSC
364 <sect1>6502X mode<label id="6502X-mode"><p>
366 6502X mode is an extension to the normal 6502 mode. In this mode, several
367 mnemonics for illegal instructions of the NMOS 6502 CPUs are accepted. Since
368 these instructions are illegal, there are no official mnemonics for them. The
369 unofficial ones are taken from <htmlurl
370 url="http://oxyron.net/graham/opcodes02.html"
371 name="http://oxyron.net/graham/opcodes02.html">. Please note that only the
372 ones marked as "stable" are supported. The following table uses information
373 from the mentioned web page, for more information, see there.
376 <item><tt>ALR: A:=(A and #{imm})*2;</tt>
377 <item><tt>ANC: A:=A and #{imm};</tt> Generates opcode $0B.
378 <item><tt>ARR: A:=(A and #{imm})/2;</tt>
379 <item><tt>AXS: X:=A and X-#{imm};</tt>
380 <item><tt>DCP: {adr}:={adr}-1; A-{adr};</tt>
381 <item><tt>ISC: {adr}:={adr}+1; A:=A-{adr};</tt>
382 <item><tt>LAS: A,X,S:={adr} and S;</tt>
383 <item><tt>LAX: A,X:={adr};</tt>
384 <item><tt>RLA: {adr}:={adr}rol; A:=A and {adr};</tt>
385 <item><tt>RRA: {adr}:={adr}ror; A:=A adc {adr};</tt>
386 <item><tt>SAX: {adr}:=A and X;</tt>
387 <item><tt>SLO: {adr}:={adr}*2; A:=A or {adr};</tt>
388 <item><tt>SRE: {adr}:={adr}/2; A:=A xor {adr};</tt>
393 <sect1>sweet16 mode<label id="sweet16-mode"><p>
395 SWEET 16 is an interpreter for a pseudo 16 bit CPU written by Steve Wozniak
396 for the Apple ][ machines. It is available in the Apple ][ ROM. ca65 can
397 generate code for this pseudo CPU when switched into sweet16 mode. The
398 following is special in sweet16 mode:
402 <item>The '@' character denotes indirect addressing and is no longer available
403 for cheap local labels. If you need cheap local labels, you will have to
404 switch to another lead character using the <tt/<ref id=".LOCALCHAR"
405 name=".LOCALCHAR">/ command.
407 <item>Registers are specified using <tt/R0/ .. <tt/R15/. In sweet16 mode,
408 these identifiers are reserved words.
412 Please note that the assembler does neither supply the interpreter needed for
413 SWEET 16 code, nor the zero page locations needed for the SWEET 16 registers,
414 nor does it call the interpreter. All this must be done by your program. Apple
415 ][ programmers do probably know how to use sweet16 mode.
417 For more information about SWEET 16, see
418 <htmlurl url="http://www.6502.org/source/interpreters/sweet16.htm"
419 name="http://www.6502.org/source/interpreters/sweet16.htm">.
422 <sect1>Number format<p>
424 For literal values, the assembler accepts the widely used number formats: A
425 preceding '$' or a trailing 'h' denotes a hex value, a preceding '%'
426 denotes a binary value, and a bare number is interpreted as a decimal. There
427 are currently no octal values and no floats.
430 <sect1>Conditional assembly<p>
432 Please note that when using the conditional directives (<tt/.IF/ and friends),
433 the input must consist of valid assembler tokens, even in <tt/.IF/ branches
434 that are not assembled. The reason for this behaviour is that the assembler
435 must still be able to detect the ending tokens (like <tt/.ENDIF/), so
436 conversion of the input stream into tokens still takes place. As a consequence
437 conditional assembly directives may <bf/not/ be used to prevent normal text
438 (used as a comment or similar) from being assembled. <p>
444 <sect1>Expression evaluation<p>
446 All expressions are evaluated with (at least) 32 bit precision. An
447 expression may contain constant values and any combination of internal and
448 external symbols. Expressions that cannot be evaluated at assembly time
449 are stored inside the object file for evaluation by the linker.
450 Expressions referencing imported symbols must always be evaluated by the
454 <sect1>Size of an expression result<p>
456 Sometimes, the assembler must know about the size of the value that is the
457 result of an expression. This is usually the case, if a decision has to be
458 made, to generate a zero page or an absolute memory references. In this
459 case, the assembler has to make some assumptions about the result of an
463 <item> If the result of an expression is constant, the actual value is
464 checked to see if it's a byte sized expression or not.
465 <item> If the expression is explicitly casted to a byte sized expression by
466 one of the '>', '<' or '^' operators, it is a byte expression.
467 <item> If this is not the case, and the expression contains a symbol,
468 explicitly declared as zero page symbol (by one of the .importzp or
469 .exportzp instructions), then the whole expression is assumed to be
471 <item> If the expression contains symbols that are not defined, and these
472 symbols are local symbols, the enclosing scopes are searched for a
473 symbol with the same name. If one exists and this symbol is defined,
474 it's attributes are used to determine the result size.
475 <item> In all other cases the expression is assumed to be word sized.
478 Note: If the assembler is not able to evaluate the expression at assembly
479 time, the linker will evaluate it and check for range errors as soon as
483 <sect1>Boolean expressions<p>
485 In the context of a boolean expression, any non zero value is evaluated as
486 true, any other value to false. The result of a boolean expression is 1 if
487 it's true, and zero if it's false. There are boolean operators with extreme
488 low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/
489 operators are shortcut operators. That is, if the result of the expression is
490 already known, after evaluating the left hand side, the right hand side is
494 <sect1>Constant expressions<p>
496 Sometimes an expression must evaluate to a constant without looking at any
497 further input. One such example is the <tt/<ref id=".IF" name=".IF">/ command
498 that decides if parts of the code are assembled or not. An expression used in
499 the <tt/.IF/ command cannot reference a symbol defined later, because the
500 decision about the <tt/.IF/ must be made at the point when it is read. If the
501 expression used in such a context contains only constant numerical values,
502 there is no problem. When unresolvable symbols are involved it may get harder
503 for the assembler to determine if the expression is actually constant, and it
504 is even possible to create expressions that aren't recognized as constant.
505 Simplifying the expressions will often help.
507 In cases where the result of the expression is not needed immediately, the
508 assembler will delay evaluation until all input is read, at which point all
509 symbols are known. So using arbitrary complex constant expressions is no
510 problem in most cases.
514 <sect1>Available operators<label id="operators"><p>
518 <bf/Operator/| <bf/Description/| <bf/Precedence/@<hline>
519 | Built-in string functions| 0@
521 | Built-in pseudo-variables| 1@
522 | Built-in pseudo-functions| 1@
523 +| Unary positive| 1@
524 -| Unary negative| 1@
526 .BITNOT| Unary bitwise not| 1@
528 .LOBYTE| Unary low-byte operator| 1@
530 .HIBYTE| Unary high-byte operator| 1@
532 .BANKBYTE| Unary bank-byte operator| 1@
534 *| Multiplication| 2@
536 .MOD| Modulo operator| 2@
538 .BITAND| Bitwise and| 2@
540 .BITXOR| Binary bitwise xor| 2@
542 .SHL| Shift-left operator| 2@
544 .SHR| Shift-right operator| 2@
546 +| Binary addition| 3@
547 -| Binary subtraction| 3@
549 .BITOR| Bitwise or| 3@
551 = | Compare operator (equal)| 4@
552 <>| Compare operator (not equal)| 4@
553 <| Compare operator (less)| 4@
554 >| Compare operator (greater)| 4@
555 <=| Compare operator (less or equal)| 4@
556 >=| Compare operator (greater or equal)| 4@
559 .AND| Boolean and| 5@
560 .XOR| Boolean xor| 5@
562 ||<newline>
566 .NOT| Boolean not| 7@<hline>
568 <caption>Available operators, sorted by precedence
571 To force a specific order of evaluation, parentheses may be used, as usual.
575 <sect>Symbols and labels<p>
577 The assembler allows you to use symbols instead of naked values to make
578 the source more readable. There are a lot of different ways to define and
579 use symbols and labels, giving a lot of flexibility.
582 <sect1>Numeric constants<p>
584 Numeric constants are defined using the equal sign or the label assignment
585 operator. After doing
591 may use the symbol "two" in every place where a number is expected, and it is
592 evaluated to the value 2 in this context. The label assignment operator causes
593 the same, but causes the symbol to be marked as a label, which may cause a
594 different handling in the debugger:
600 The right side can of course be an expression:
607 <sect1>Standard labels<p>
609 A label is defined by writing the name of the label at the start of the line
610 (before any instruction mnemonic, macro or pseudo directive), followed by a
611 colon. This will declare a symbol with the given name and the value of the
612 current program counter.
615 <sect1>Local labels and symbols<p>
617 Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to
618 create regions of code where the names of labels and symbols are local to this
619 region. They are not known outside of this region and cannot be accessed from
620 there. Such regions may be nested like PROCEDUREs in Pascal.
622 See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
623 directive for more information.
626 <sect1>Cheap local labels<p>
628 Cheap local labels are defined like standard labels, but the name of the
629 label must begin with a special symbol (usually '@', but this can be
630 changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt>
633 Cheap local labels are visible only between two non cheap labels. As soon as a
634 standard symbol is encountered (this may also be a local symbol if inside a
635 region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the
636 cheap local symbol goes out of scope.
638 You may use cheap local labels as an easy way to reuse common label
639 names like "Loop". Here is an example:
642 Clear: lda #$00 ; Global label
644 @Loop: sta Mem,y ; Local label
648 Sub: ... ; New global label
649 bne @Loop ; ERROR: Unknown identifier!
652 <sect1>Unnamed labels<p>
654 If you really want to write messy code, there are also unnamed labels. These
655 labels do not have a name (you guessed that already, didn't you?). A colon is
656 used to mark the absence of the name.
658 Unnamed labels may be accessed by using the colon plus several minus or plus
659 characters as a label designator. Using the '-' characters will create a back
660 reference (use the n'th label backwards), using '+' will create a forward
661 reference (use the n'th label in forward direction). An example will help to
684 As you can see from the example, unnamed labels will make even short
685 sections of code hard to understand, because you have to count labels
686 to find branch targets (this is the reason why I for my part do
687 prefer the "cheap" local labels). Nevertheless, unnamed labels are
688 convenient in some situations, so it's your decision.
691 <sect1>Using macros to define labels and constants<p>
693 While there are drawbacks with this approach, it may be handy in some
694 situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is
695 possible to define symbols or constants that may be used elsewhere. Since
696 the macro facility works on a very low level, there is no scoping. On the
697 other side, you may also define string constants this way (this is not
698 possible with the other symbol types).
704 .DEFINE version "SOS V2.3"
706 four = two * two ; Ok
709 .PROC ; Start local scope
710 two = 3 ; Will give "2 = 3" - invalid!
715 <sect1>Symbols and <tt>.DEBUGINFO</tt><p>
717 If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref
718 id="option-g" name="-g"> is given on the command line), global, local and
719 cheap local labels are written to the object file and will be available in the
720 symbol file via the linker. Unnamed labels are not written to the object file,
721 because they don't have a name which would allow to access them.
725 <sect>Scopes<label id="scopes"><p>
727 ca65 implements several sorts of scopes for symbols.
729 <sect1>Global scope<p>
731 All (non cheap local) symbols that are declared outside of any nested scopes
735 <sect1>Cheap locals<p>
737 A special scope is the scope for cheap local symbols. It lasts from one non
738 local symbol to the next one, without any provisions made by the programmer.
739 All other scopes differ in usage but use the same concept internally.
742 <sect1>Generic nested scopes<p>
744 A nested scoped for generic use is started with <tt/<ref id=".SCOPE"
745 name=".SCOPE">/ and closed with <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/.
746 The scope can have a name, in which case it is accessible from the outside by
747 using <ref id="scopesyntax" name="explicit scopes">. If the scope does not
748 have a name, all symbols created within the scope are local to the scope, and
749 aren't accessible from the outside.
751 A nested scope can access symbols from the local or from enclosing scopes by
752 name without using explicit scope names. In some cases there may be
753 ambiguities, for example if there is a reference to a local symbol that is not
754 yet defined, but a symbol with the same name exists in outer scopes:
766 In the example above, the <tt/lda/ instruction will load the value 3 into the
767 accumulator, because <tt/foo/ is redefined in the scope. However:
779 Here, <tt/lda/ will still load from <tt/$12,x/, but since it is unknown to the
780 assembler that <tt/foo/ is a zeropage symbol when translating the instruction,
781 absolute mode is used instead. In fact, the assembler will not use absolute
782 mode by default, but it will search through the enclosing scopes for a symbol
783 with the given name. If one is found, the address size of this symbol is used.
784 This may lead to errors:
796 In this case, when the assembler sees the symbol <tt/foo/ in the <tt/lda/
797 instruction, it will search for an already defined symbol <tt/foo/. It will
798 find <tt/foo/ in scope <tt/outer/, and a close look reveals that it is a
799 zeropage symbol. So the assembler will use zeropage addressing mode. If
800 <tt/foo/ is redefined later in scope <tt/inner/, the assembler tries to change
801 the address in the <tt/lda/ instruction already translated, but since the new
802 value needs absolute addressing mode, this fails, and an error message "Range
805 Of course the most simple solution for the problem is to move the definition
806 of <tt/foo/ in scope <tt/inner/ upwards, so it precedes its use. There may be
807 rare cases when this cannot be done. In these cases, you can use one of the
808 address size override operators:
820 This will cause the <tt/lda/ instruction to be translated using absolute
821 addressing mode, which means changing the symbol reference later does not
825 <sect1>Nested procedures<p>
827 A nested procedure is created by use of <tt/<ref id=".PROC" name=".PROC">/. It
828 differs from a <tt/<ref id=".SCOPE" name=".SCOPE">/ in that it must have a
829 name, and a it will introduce a symbol with this name in the enclosing scope.
838 is actually the same as
847 This is the reason why a procedure must have a name. If you want a scope
848 without a name, use <tt/<ref id=".SCOPE" name=".SCOPE">/.
850 <bf/Note:/ As you can see from the example above, scopes and symbols live in
851 different namespaces. There can be a symbol named <tt/foo/ and a scope named
852 <tt/foo/ without any conflicts (but see the section titled <ref
853 id="scopesearch" name=""Scope search order"">).
856 <sect1>Structs, unions and enums<p>
858 Structs, unions and enums are explained in a <ref id="structs" name="separate
859 section">, I do only cover them here, because if they are declared with a
860 name, they open a nested scope, similar to <tt/<ref id=".SCOPE"
861 name=".SCOPE">/. However, when no name is specified, the behaviour is
862 different: In this case, no new scope will be opened, symbols declared within
863 a struct, union, or enum declaration will then be added to the enclosing scope
867 <sect1>Explicit scope specification<label id="scopesyntax"><p>
869 Accessing symbols from other scopes is possible by using an explicit scope
870 specification, provided that the scope where the symbol lives in has a name.
871 The namespace token (<tt/::/) is used to access other scopes:
879 lda foo::bar ; Access foo in scope bar
882 The only way to deny access to a scope from the outside is to declare a scope
883 without a name (using the <tt/<ref id=".SCOPE" name=".SCOPE">/ command).
885 A special syntax is used to specify the global scope: If a symbol or scope is
886 preceded by the namespace token, the global scope is searched:
893 lda #::bar ; Access the global bar (which is 3)
898 <sect1>Scope search order<label id="scopesearch"><p>
900 The assembler searches for a scope in a similar way as for a symbol. First, it
901 looks in the current scope, and then it walks up the enclosing scopes until
904 However, one important thing to note when using explicit scope syntax is, that
905 a symbol may be accessed before it is defined, but a scope may <bf/not/ be
906 used without a preceding definition. This means that in the following
915 lda #foo::bar ; Will load 3, not 2!
922 the reference to the scope <tt/foo/ will use the global scope, and not the
923 local one, because the local one is not visible at the point where it is
926 Things get more complex if a complete chain of scopes is specified:
937 lda #outer::inner::bar ; 1
949 When <tt/outer::inner::bar/ is referenced in the <tt/lda/ instruction, the
950 assembler will first search in the local scope for a scope named <tt/outer/.
951 Since none is found, the enclosing scope (<tt/another/) is checked. There is
952 still no scope named <tt/outer/, so scope <tt/foo/ is checked, and finally
953 scope <tt/outer/ is found. Within this scope, <tt/inner/ is searched, and in
954 this scope, the assembler looks for a symbol named <tt/bar/.
956 Please note that once the anchor scope is found, all following scopes
957 (<tt/inner/ in this case) are expected to be found exactly in this scope. The
958 assembler will search the scope tree only for the first scope (if it is not
959 anchored in the root scope). Starting from there on, there is no flexibility,
960 so if the scope named <tt/outer/ found by the assembler does not contain a
961 scope named <tt/inner/, this would be an error, even if such a pair does exist
962 (one level up in global scope).
964 Ambiguities that may be introduced by this search algorithm may be removed by
965 anchoring the scope specification in the global scope. In the example above,
966 if you want to access the "other" symbol <tt/bar/, you would have to write:
977 lda #::outer::inner::bar ; 2
990 <sect>Address sizes and memory models<label id="address-sizes"><p>
992 <sect1>Address sizes<p>
994 ca65 assigns each segment and each symbol an address size. This is true, even
995 if the symbol is not used as an address. You may also think of a value range
996 of the symbol instead of an address size.
998 Possible address sizes are:
1001 <item>Zeropage or direct (8 bits)
1002 <item>Absolute (16 bits)
1004 <item>Long (32 bits)
1007 Since the assembler uses default address sizes for the segments and symbols,
1008 it is usually not necessary to override the default behaviour. In cases, where
1009 it is necessary, the following keywords may be used to specify address sizes:
1012 <item>DIRECT, ZEROPAGE or ZP for zeropage addressing (8 bits).
1013 <item>ABSOLUTE, ABS or NEAR for absolute addressing (16 bits).
1014 <item>FAR for far addressing (24 bits).
1015 <item>LONG or DWORD for long addressing (32 bits).
1019 <sect1>Address sizes of segments<p>
1021 The assembler assigns an address size to each segment. Since the
1022 representation of a label within this segment is "segment start + offset",
1023 labels will inherit the address size of the segment they are declared in.
1025 The address size of a segment may be changed, by using an optional address
1026 size modifier. See the <tt/<ref id=".SEGMENT" name="segment directive">/ for
1027 an explanation on how this is done.
1030 <sect1>Address sizes of symbols<p>
1035 <sect1>Memory models<p>
1037 The default address size of a segment depends on the memory model used. Since
1038 labels inherit the address size from the segment they are declared in,
1039 changing the memory model is an easy way to change the address size of many
1045 <sect>Pseudo variables<label id="pseudo-variables"><p>
1047 Pseudo variables are readable in all cases, and in some special cases also
1050 <sect1><tt>*</tt><p>
1052 Reading this pseudo variable will return the program counter at the start
1053 of the current input line.
1055 Assignment to this variable is possible when <tt/<ref id=".FEATURE"
1056 name=".FEATURE pc_assignment">/ is used. Note: You should not use
1057 assignments to <tt/*/, use <tt/<ref id=".ORG" name=".ORG">/ instead.
1060 <sect1><tt>.CPU</tt><label id=".CPU"><p>
1062 Reading this pseudo variable will give a constant integer value that
1063 tells which CPU is currently enabled. It can also tell which instruction
1064 set the CPU is able to translate. The value read from the pseudo variable
1065 should be further examined by using one of the constants defined by the
1066 "cpu" macro package (see <tt/<ref id=".MACPACK" name=".MACPACK">/).
1068 It may be used to replace the .IFPxx pseudo instructions or to construct
1069 even more complex expressions.
1075 .if (.cpu .bitand CPU_ISET_65816)
1087 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
1089 This builtin pseudo variable is only available in macros. It is replaced by
1090 the actual number of parameters that were given in the macro invocation.
1095 .macro foo arg1, arg2, arg3
1096 .if .paramcount <> 3
1097 .error "Too few parameters for macro foo"
1103 See section <ref id="macros" name="Macros">.
1106 <sect1><tt>.TIME</tt><label id=".TIME"><p>
1108 Reading this pseudo variable will give a constant integer value that
1109 represents the current time in POSIX standard (as seconds since the
1112 It may be used to encode the time of translation somewhere in the created
1118 .dword .time ; Place time here
1122 <sect1><tt>.VERSION</tt><label id=".VERSION"><p>
1124 Reading this pseudo variable will give the assembler version according to
1125 the following formula:
1127 VER_MAJOR*$100 + VER_MINOR*$10 + VER_PATCH
1129 It may be used to encode the assembler version or check the assembler for
1130 special features not available with older versions.
1134 Version 2.11.1 of the assembler will return $2B1 as numerical constant when
1135 reading the pseudo variable <tt/.VERSION/.
1139 <sect>Pseudo functions<label id="pseudo-functions"><p>
1141 Pseudo functions expect their arguments in parenthesis, and they have a result,
1142 either a string or an expression.
1145 <sect1><tt>.BANKBYTE</tt><label id=".BANKBYTE"><p>
1147 The function returns the bank byte (that is, bits 16-23) of its argument.
1148 It works identical to the '^' operator.
1150 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1151 <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>
1154 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
1156 Builtin function. The function evaluates its argument in braces and yields
1157 "false" if the argument is non blank (there is an argument), and "true" if
1158 there is no argument. The token list that makes up the function argument
1159 may optionally be enclosed in curly braces. This allows the inclusion of
1160 tokens that would otherwise terminate the list (the closing right
1161 parenthesis). The curly braces are not considered part of the list, a list
1162 just consisting of curly braces is considered to be empty.
1164 As an example, the <tt/.IFBLANK/ statement may be replaced by
1172 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
1174 Builtin string function. The function allows to concatenate a list of string
1175 constants separated by commas. The result is a string constant that is the
1176 concatenation of all arguments. This function is most useful in macros and
1177 when used together with the <tt/.STRING/ builtin function. The function may
1178 be used in any case where a string constant is expected.
1183 .include .concat ("myheader", ".", "inc")
1186 This is the same as the command
1189 .include "myheader.inc"
1193 <sect1><tt>.CONST</tt><label id=".CONST"><p>
1195 Builtin function. The function evaluates its argument in braces and
1196 yields "true" if the argument is a constant expression (that is, an
1197 expression that yields a constant value at assembly time) and "false"
1198 otherwise. As an example, the .IFCONST statement may be replaced by
1205 <sect1><tt>.HIBYTE</tt><label id=".HIBYTE"><p>
1207 The function returns the high byte (that is, bits 8-15) of its argument.
1208 It works identical to the '>' operator.
1210 See: <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>,
1211 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1214 <sect1><tt>.HIWORD</tt><label id=".HIWORD"><p>
1216 The function returns the high word (that is, bits 16-31) of its argument.
1218 See: <tt><ref id=".LOWORD" name=".LOWORD"></tt>
1221 <sect1><tt>.IDENT</tt><label id=".IDENT"><p>
1223 The function expects a string as its argument, and converts this argument
1224 into an identifier. If the string starts with the current <tt/<ref
1225 id=".LOCALCHAR" name=".LOCALCHAR">/, it will be converted into a cheap local
1226 identifier, otherwise it will be converted into a normal identifier.
1231 .macro makelabel arg1, arg2
1232 .ident (.concat (arg1, arg2)):
1235 makelabel "foo", "bar"
1237 .word foobar ; Valid label
1241 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1243 Builtin function. Extracts the left part of a given token list.
1248 .LEFT (<int expr>, <token list>)
1251 The first integer expression gives the number of tokens to extract from
1252 the token list. The second argument is the token list itself. The token
1253 list may optionally be enclosed into curly braces. This allows the
1254 inclusion of tokens that would otherwise terminate the list (the closing
1255 right paren in the given case).
1259 To check in a macro if the given argument has a '#' as first token
1260 (immediate addressing mode), use something like this:
1265 .if (.match (.left (1, {arg}), #))
1267 ; ldax called with immediate operand
1275 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1276 name=".RIGHT"></tt> builtin functions.
1279 <sect1><tt>.LOBYTE</tt><label id=".LOBYTE"><p>
1281 The function returns the low byte (that is, bits 0-7) of its argument.
1282 It works identical to the '<' operator.
1284 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1285 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1288 <sect1><tt>.LOWORD</tt><label id=".LOWORD"><p>
1290 The function returns the low word (that is, bits 0-15) of its argument.
1292 See: <tt><ref id=".HIWORD" name=".HIWORD"></tt>
1295 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1297 Builtin function. Matches two token lists against each other. This is
1298 most useful within macros, since macros are not stored as strings, but
1304 .MATCH(<token list #1>, <token list #2>)
1307 Both token list may contain arbitrary tokens with the exception of the
1308 terminator token (comma resp. right parenthesis) and
1315 The token lists may optionally be enclosed into curly braces. This allows
1316 the inclusion of tokens that would otherwise terminate the list (the closing
1317 right paren in the given case). Often a macro parameter is used for any of
1320 Please note that the function does only compare tokens, not token
1321 attributes. So any number is equal to any other number, regardless of the
1322 actual value. The same is true for strings. If you need to compare tokens
1323 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1324 name=".XMATCH"></tt> function.
1328 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1329 while honoring the sign bit. The builtin processor instructions will allow
1330 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1331 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1332 to check for this and print and error for invalid calls.
1337 .if (.not .blank(arg)) .and (.not .match ({arg}, a))
1338 .error "Syntax error"
1341 cmp #$80 ; Bit 7 into carry
1342 lsr a ; Shift carry into bit 7
1347 The macro will only accept no arguments, or one argument that must be the
1348 reserved keyword "A".
1350 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1353 <sect1><tt>.MID</tt><label id=".MID"><p>
1355 Builtin function. Takes a starting index, a count and a token list as
1356 arguments. Will return part of the token list.
1361 .MID (<int expr>, <int expr>, <token list>)
1364 The first integer expression gives the starting token in the list (the first
1365 token has index 0). The second integer expression gives the number of tokens
1366 to extract from the token list. The third argument is the token list itself.
1367 The token list may optionally be enclosed into curly braces. This allows the
1368 inclusion of tokens that would otherwise terminate the list (the closing
1369 right paren in the given case).
1373 To check in a macro if the given argument has a '<tt/#/' as first token
1374 (immediate addressing mode), use something like this:
1379 .if (.match (.mid (0, 1, {arg}), #))
1381 ; ldax called with immediate operand
1389 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1390 name=".RIGHT"></tt> builtin functions.
1393 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
1395 Builtin function. The function expects an identifier as argument in braces.
1396 The argument is evaluated, and the function yields "true" if the identifier
1397 is a symbol that has already been referenced somewhere in the source file up
1398 to the current position. Otherwise the function yields false. As an example,
1399 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
1405 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1408 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
1410 Builtin function. Extracts the right part of a given token list.
1415 .RIGHT (<int expr>, <token list>)
1418 The first integer expression gives the number of tokens to extract from the
1419 token list. The second argument is the token list itself. The token list
1420 may optionally be enclosed into curly braces. This allows the inclusion of
1421 tokens that would otherwise terminate the list (the closing right paren in
1424 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
1425 name=".MID"></tt> builtin functions.
1428 <sect1><tt>.SIZEOF</tt><label id=".SIZEOF"><p>
1430 <tt/.SIZEOF/ is a pseudo function that returns the size of its argument. The
1431 argument can be a struct/union, a struct member, a procedure, or a label. In
1432 case of a procedure or label, its size is defined by the amount of data
1433 placed in the segment where the label is relative to. If a line of code
1434 switches segments (for example in a macro) data placed in other segments
1435 does not count for the size.
1437 Please note that a symbol or scope must exist, before it is used together with
1438 <tt/.SIZEOF/ (this may get relaxed later, but will always be true for scopes).
1439 A scope has preference over a symbol with the same name, so if the last part
1440 of a name represents both, a scope and a symbol, the scope is chosen over the
1443 After the following code:
1446 .struct Point ; Struct size = 4
1451 P: .tag Point ; Declare a point
1452 @P: .tag Point ; Declare another point
1464 .data ; Segment switch!!!
1470 <tag><tt/.sizeof(Point)/</tag>
1471 will have the value 4, because this is the size of struct <tt/Point/.
1473 <tag><tt/.sizeof(Point::xcoord)/</tag>
1474 will have the value 2, because this is the size of the member <tt/xcoord/
1475 in struct <tt/Point/.
1477 <tag><tt/.sizeof(P)/</tag>
1478 will have the value 4, this is the size of the data declared on the same
1479 source line as the label <tt/P/, which is in the same segment that <tt/P/
1482 <tag><tt/.sizeof(@P)/</tag>
1483 will have the value 4, see above. The example demonstrates that <tt/.SIZEOF/
1484 does also work for cheap local symbols.
1486 <tag><tt/.sizeof(Code)/</tag>
1487 will have the value 3, since this is amount of data emitted into the code
1488 segment, the segment that was active when <tt/Code/ was entered. Note that
1489 this value includes the amount of data emitted in child scopes (in this
1490 case <tt/Code::Inner/).
1492 <tag><tt/.sizeof(Code::Inner)/</tag>
1493 will have the value 1 as expected.
1495 <tag><tt/.sizeof(Data)/</tag>
1496 will have the value 0. Data is emitted within the scope <tt/Data/, but since
1497 the segment is switched after entry, this data is emitted into another
1502 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
1504 Builtin function. The function accepts a string and an index as
1505 arguments and returns the value of the character at the given position
1506 as an integer value. The index is zero based.
1512 ; Check if the argument string starts with '#'
1513 .if (.strat (Arg, 0) = '#')
1520 <sect1><tt>.SPRINTF</tt><label id=".SPRINTF"><p>
1522 Builtin function. It expects a format string as first argument. The number
1523 and type of the following arguments depend on the format string. The format
1524 string is similar to the one of the C <tt/printf/ function. Missing things
1525 are: Length modifiers, variable width.
1527 The result of the function is a string.
1534 ; Generate an identifier:
1535 .ident (.sprintf ("%s%03d", "label", num)):
1539 <sect1><tt>.STRING</tt><label id=".STRING"><p>
1541 Builtin function. The function accepts an argument in braces and converts
1542 this argument into a string constant. The argument may be an identifier, or
1543 a constant numeric value.
1545 Since you can use a string in the first place, the use of the function may
1546 not be obvious. However, it is useful in macros, or more complex setups.
1551 ; Emulate other assemblers:
1553 .segment .string(name)
1558 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
1560 Builtin function. The function accepts a string argument in braces and
1561 evaluates to the length of the string.
1565 The following macro encodes a string as a pascal style string with
1566 a leading length byte.
1570 .byte .strlen(Arg), Arg
1575 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
1577 Builtin function. The function accepts a token list in braces. The function
1578 result is the number of tokens given as argument. The token list may
1579 optionally be enclosed into curly braces which are not considered part of
1580 the list and not counted. Enclosement in curly braces allows the inclusion
1581 of tokens that would otherwise terminate the list (the closing right paren
1586 The <tt/ldax/ macro accepts the '#' token to denote immediate addressing (as
1587 with the normal 6502 instructions). To translate it into two separate 8 bit
1588 load instructions, the '#' token has to get stripped from the argument:
1592 .if (.match (.mid (0, 1, {arg}), #))
1593 ; ldax called with immediate operand
1594 lda #<(.right (.tcount ({arg})-1, {arg}))
1595 ldx #>(.right (.tcount ({arg})-1, {arg}))
1603 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
1605 Builtin function. Matches two token lists against each other. This is
1606 most useful within macros, since macros are not stored as strings, but
1612 .XMATCH(<token list #1>, <token list #2>)
1615 Both token list may contain arbitrary tokens with the exception of the
1616 terminator token (comma resp. right parenthesis) and
1623 The token lists may optionally be enclosed into curly braces. This allows
1624 the inclusion of tokens that would otherwise terminate the list (the closing
1625 right paren in the given case). Often a macro parameter is used for any of
1628 The function compares tokens <em/and/ token values. If you need a function
1629 that just compares the type of tokens, have a look at the <tt><ref
1630 id=".MATCH" name=".MATCH"></tt> function.
1632 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
1636 <sect>Control commands<label id="control-commands"><p>
1638 Here's a list of all control commands and a description, what they do:
1641 <sect1><tt>.A16</tt><label id=".A16"><p>
1643 Valid only in 65816 mode. Switch the accumulator to 16 bit.
1645 Note: This command will not emit any code, it will tell the assembler to
1646 create 16 bit operands for immediate accumulator addressing mode.
1648 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1651 <sect1><tt>.A8</tt><label id=".A8"><p>
1653 Valid only in 65816 mode. Switch the accumulator to 8 bit.
1655 Note: This command will not emit any code, it will tell the assembler to
1656 create 8 bit operands for immediate accu addressing mode.
1658 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1661 <sect1><tt>.ADDR</tt><label id=".ADDR"><p>
1663 Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and
1664 may be used for better readability if the data words are address values. In
1665 65816 mode, the address is forced to be 16 bit wide to fit into the current
1666 segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command
1667 must be followed by a sequence of (not necessarily constant) expressions.
1672 .addr $0D00, $AF13, _Clear
1675 See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD"
1679 <sect1><tt>.ALIGN</tt><label id=".ALIGN"><p>
1681 Align data to a given boundary. The command expects a constant integer
1682 argument that must be a power of two, plus an optional second argument
1683 in byte range. If there is a second argument, it is used as fill value,
1684 otherwise the value defined in the linker configuration file is used
1685 (the default for this value is zero).
1687 Since alignment depends on the base address of the module, you must
1688 give the same (or a greater) alignment for the segment when linking.
1689 The linker will give you a warning, if you don't do that.
1698 <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"><p>
1700 Define a string with a trailing zero.
1705 Msg: .asciiz "Hello world"
1708 This will put the string "Hello world" followed by a binary zero into
1709 the current segment. There may be more strings separated by commas, but
1710 the binary zero is only appended once (after the last one).
1713 <sect1><tt>.ASSERT</tt><label id=".ASSERT"><p>
1715 Add an assertion. The command is followed by an expression, an action
1716 specifier, and an optional message that is output in case the assertion
1717 fails. If no message was given, the string "Assertion failed" is used. The
1718 action specifier may be one of <tt/warning/ or <tt/error/. The assertion is
1719 evaluated by the assembler if possible, and also passed to the linker in the
1720 object file (if one is generated). The linker will then evaluate the
1721 expression when segment placement has been done.
1726 .assert * = $8000, error, "Code not at $8000"
1729 The example assertion will check that the current location is at $8000,
1730 when the output file is written, and abort with an error if this is not
1731 the case. More complex expressions are possible. The action specifier
1732 <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs
1733 an error message. In the latter case, generation if the output file is
1734 suppressed in both the assembler and linker.
1737 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
1739 Is followed by a plus or a minus character. When switched on (using a
1740 +), undefined symbols are automatically marked as import instead of
1741 giving errors. When switched off (which is the default so this does not
1742 make much sense), this does not happen and an error message is
1743 displayed. The state of the autoimport flag is evaluated when the
1744 complete source was translated, before outputting actual code, so it is
1745 <em/not/ possible to switch this feature on or off for separate sections
1746 of code. The last setting is used for all symbols.
1748 You should probably not use this switch because it delays error
1749 messages about undefined symbols until the link stage. The cc65
1750 compiler (which is supposed to produce correct assembler code in all
1751 circumstances, something which is not true for most assembler
1752 programmers) will insert this command to avoid importing each and every
1753 routine from the runtime library.
1758 .autoimport + ; Switch on auto import
1762 <sect1><tt>.BSS</tt><label id=".BSS"><p>
1764 Switch to the BSS segment. The name of the BSS segment is always "BSS",
1765 so this is a shortcut for
1771 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1774 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
1776 Define byte sized data. Must be followed by a sequence of (byte ranged)
1777 expressions or strings.
1783 .byt "world", $0D, $00
1787 <sect1><tt>.CASE</tt><label id=".CASE"><p>
1789 Switch on or off case sensitivity on identifiers. The default is off
1790 (that is, identifiers are case sensitive), but may be changed by the
1791 -i switch on the command line.
1792 The command must be followed by a '+' or '-' character to switch the
1793 option on or off respectively.
1798 .case - ; Identifiers are not case sensitive
1802 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
1804 Apply a custom mapping for characters. The command is followed by two
1805 numbers in the range 1..255. The first one is the index of the source
1806 character, the second one is the mapping. The mapping applies to all
1807 character and string constants when they generate output, and overrides
1808 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
1809 command line switch.
1814 .charmap $41, $61 ; Map 'A' to 'a'
1818 <sect1><tt>.CODE</tt><label id=".CODE"><p>
1820 Switch to the CODE segment. The name of the CODE segment is always
1821 "CODE", so this is a shortcut for
1827 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1830 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
1832 Export a symbol and mark it in a special way. The linker is able to build
1833 tables of all such symbols. This may be used to automatically create a list
1834 of functions needed to initialize linked library modules.
1836 Note: The linker has a feature to build a table of marked routines, but it
1837 is your code that must call these routines, so just declaring a symbol with
1838 <tt/.CONDES/ does nothing by itself.
1840 All symbols are exported as an absolute (16 bit) symbol. You don't need to
1841 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
1842 is implied by <tt/.CONDES/.
1844 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
1845 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
1846 specifying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
1847 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
1848 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
1849 name=".INTERRUPTOR"></tt> commands are actually shortcuts for <tt/.CONDES/
1850 with a type of <tt/constructor/ resp. <tt/destructor/ or <tt/interruptor/.
1852 After the type, an optional priority may be specified. Higher numeric values
1853 mean higher priority. If no priority is given, the default priority of 7 is
1854 used. Be careful when assigning priorities to your own module constructors
1855 so they won't interfere with the ones in the cc65 library.
1860 .condes ModuleInit, constructor
1861 .condes ModInit, 0, 16
1864 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
1865 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
1866 name=".INTERRUPTOR"></tt> commands and the separate section <ref id="condes"
1867 name="Module constructors/destructors"> explaining the feature in more
1871 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
1873 Export a symbol and mark it as a module constructor. This may be used
1874 together with the linker to build a table of constructor subroutines that
1875 are called by the startup code.
1877 Note: The linker has a feature to build a table of marked routines, but it
1878 is your code that must call these routines, so just declaring a symbol as
1879 constructor does nothing by itself.
1881 A constructor is always exported as an absolute (16 bit) symbol. You don't
1882 need to use an additional <tt/.export/ statement, this is implied by
1883 <tt/.constructor/. It may have an optional priority that is separated by a
1884 comma. Higher numeric values mean a higher priority. If no priority is
1885 given, the default priority of 7 is used. Be careful when assigning
1886 priorities to your own module constructors so they won't interfere with the
1887 ones in the cc65 library.
1892 .constructor ModuleInit
1893 .constructor ModInit, 16
1896 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1897 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
1898 <ref id="condes" name="Module constructors/destructors"> explaining the
1899 feature in more detail.
1902 <sect1><tt>.DATA</tt><label id=".DATA"><p>
1904 Switch to the DATA segment. The name of the DATA segment is always
1905 "DATA", so this is a shortcut for
1911 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1914 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
1916 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
1917 create word sized data in native 65XX format). Must be followed by a
1918 sequence of (word ranged) expressions.
1926 This will emit the bytes
1932 into the current segment in that order.
1935 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
1937 Switch on or off debug info generation. The default is off (that is,
1938 the object file will not contain debug infos), but may be changed by the
1939 -g switch on the command line.
1940 The command must be followed by a '+' or '-' character to switch the
1941 option on or off respectively.
1946 .debuginfo + ; Generate debug info
1950 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
1952 Start a define style macro definition. The command is followed by an
1953 identifier (the macro name) and optionally by a list of formal arguments
1955 See section <ref id="macros" name="Macros">.
1958 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
1960 Builtin function. The function expects an identifier as argument in braces.
1961 The argument is evaluated, and the function yields "true" if the identifier
1962 is a symbol that is already defined somewhere in the source file up to the
1963 current position. Otherwise the function yields false. As an example, the
1964 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
1971 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
1973 Export a symbol and mark it as a module destructor. This may be used
1974 together with the linker to build a table of destructor subroutines that
1975 are called by the startup code.
1977 Note: The linker has a feature to build a table of marked routines, but it
1978 is your code that must call these routines, so just declaring a symbol as
1979 constructor does nothing by itself.
1981 A destructor is always exported as an absolute (16 bit) symbol. You don't
1982 need to use an additional <tt/.export/ statement, this is implied by
1983 <tt/.destructor/. It may have an optional priority that is separated by a
1984 comma. Higher numerical values mean a higher priority. If no priority is
1985 given, the default priority of 7 is used. Be careful when assigning
1986 priorities to your own module destructors so they won't interfere with the
1987 ones in the cc65 library.
1992 .destructor ModuleDone
1993 .destructor ModDone, 16
1996 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1997 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
1998 section <ref id="condes" name="Module constructors/destructors"> explaining
1999 the feature in more detail.
2002 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
2004 Define dword sized data (4 bytes) Must be followed by a sequence of
2010 .dword $12344512, $12FA489
2014 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
2016 Conditional assembly: Reverse the current condition.
2019 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
2021 Conditional assembly: Reverse current condition and test a new one.
2024 <sect1><tt>.END</tt><label id=".END"><p>
2026 Forced end of assembly. Assembly stops at this point, even if the command
2027 is read from an include file.
2030 <sect1><tt>.ENDENUM</tt><label id=".ENDENUM"><p>
2032 End a <tt><ref id=".ENUM" name=".ENUM"></tt> declaration.
2035 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
2037 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
2038 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
2041 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
2043 End of macro definition (see section <ref id="macros" name="Macros">).
2046 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
2048 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
2051 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
2053 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
2056 <sect1><tt>.ENDSCOPE</tt><label id=".ENDSCOPE"><p>
2058 End of local lexical level (see <tt/<ref id=".SCOPE" name=".SCOPE">/).
2061 <sect1><tt>.ENDSTRUCT</tt><label id=".ENDSTRUCT"><p>
2063 Ends a struct definition. See the <tt/<ref id=".STRUCT" name=".STRUCT">/
2064 command and the separate section named <ref id="structs" name=""Structs
2068 <sect1><tt>.ENUM</tt><label id=".ENUM"><p>
2070 Start an enumeration. This directive is very similar to the C <tt/enum/
2071 keyword. If a name is given, a new scope is created for the enumeration,
2072 otherwise the enumeration members are placed in the enclosing scope.
2074 In the enumeration body, symbols are declared. The first symbol has a value
2075 of zero, and each following symbol will get the value of the preceding plus
2076 one. This behaviour may be overridden by an explicit assignment. Two symbols
2077 may have the same value.
2089 Above example will create a new scope named <tt/errorcodes/ with three
2090 symbols in it that get the values 0, 1 and 2 respectively. Another way
2091 to write this would have been:
2101 Please note that explicit scoping must be used to access the identifiers:
2104 .word errorcodes::no_error
2107 A more complex example:
2116 EWOULDBLOCK = EAGAIN
2120 In this example, the enumeration does not have a name, which means that the
2121 members will be visible in the enclosing scope and can be used in this scope
2122 without explicit scoping. The first member (<tt/EUNKNOWN/) has the value -1.
2123 The value for the following members is incremented by one, so <tt/EOK/ would
2124 be zero and so on. <tt/EWOULDBLOCK/ is an alias for <tt/EGAIN/, so it has an
2125 override for the value using an already defined symbol.
2128 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
2130 Force an assembly error. The assembler will output an error message
2131 preceded by "User error" and will <em/not/ produce an object file.
2133 This command may be used to check for initial conditions that must be
2134 set before assembling a source file.
2144 .error "Must define foo or bar!"
2148 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
2149 id=".OUT" name=".OUT"></tt> directives.
2152 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
2154 Abort a macro expansion immediately. This command is often useful in
2155 recursive macros. See separate section <ref id="macros" name="Macros">.
2158 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
2160 Make symbols accessible from other modules. Must be followed by a comma
2161 separated list of symbols to export, with each one optionally followed by an
2162 address specification and (also optional) an assignment. Using an additional
2163 assignment in the export statement allows to define and export a symbol in
2164 one statement. The default is to export the symbol with the address size it
2165 actually has. The assembler will issue a warning, if the symbol is exported
2166 with an address size smaller than the actual address size.
2173 .export foobar: far = foo * bar
2174 .export baz := foobar, zap: far = baz - bar
2177 As with constant definitions, using <tt/:=/ instead of <tt/=/ marks the
2180 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
2183 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
2185 Make symbols accessible from other modules. Must be followed by a comma
2186 separated list of symbols to export. The exported symbols are explicitly
2187 marked as zero page symbols. An assignment may be included in the
2188 <tt/.EXPORTZP/ statement. This allows to define and export a symbol in one
2195 .exportzp baz := $02
2198 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
2201 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
2203 Define far (24 bit) address data. The command must be followed by a
2204 sequence of (not necessarily constant) expressions.
2209 .faraddr DrawCircle, DrawRectangle, DrawHexagon
2212 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
2215 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
2217 This directive may be used to enable one or more compatibility features
2218 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
2219 possible, it may be useful when porting sources written for other
2220 assemblers. There is no way to switch a feature off, once you have
2221 enabled it, so using
2227 will enable the feature until end of assembly is reached.
2229 The following features are available:
2233 <tag><tt>at_in_identifiers</tt></tag>
2235 Accept the at character (`@') as a valid character in identifiers. The
2236 at character is not allowed to start an identifier, even with this
2239 <tag><tt>c_comments</tt></tag>
2241 Allow C like comments using <tt>/*</tt> and <tt>*/</tt> as left and right
2242 comment terminators. Note that C comments may not be nested. There's also a
2243 pitfall when using C like comments: All statements must be terminated by
2244 "end-of-line". Using C like comments, it is possible to hide the newline,
2245 which results in error messages. See the following non working example:
2248 lda #$00 /* This comment hides the newline
2252 <tag><tt>dollar_in_identifiers</tt></tag>
2254 Accept the dollar sign (`$') as a valid character in identifiers. The
2255 at character is not allowed to start an identifier, even with this
2258 <tag><tt>dollar_is_pc</tt></tag>
2260 The dollar sign may be used as an alias for the star (`*'), which
2261 gives the value of the current PC in expressions.
2262 Note: Assignment to the pseudo variable is not allowed.
2264 <tag><tt>labels_without_colons</tt></tag>
2266 Allow labels without a trailing colon. These labels are only accepted,
2267 if they start at the beginning of a line (no leading white space).
2269 <tag><tt>leading_dot_in_identifiers</tt></tag>
2271 Accept the dot (`.') as the first character of an identifier. This may be
2272 used for example to create macro names that start with a dot emulating
2273 control directives of other assemblers. Note however, that none of the
2274 reserved keywords built into the assembler, that starts with a dot, may be
2275 overridden. When using this feature, you may also get into trouble if
2276 later versions of the assembler define new keywords starting with a dot.
2278 <tag><tt>loose_char_term</tt></tag>
2280 Accept single quotes as well as double quotes as terminators for char
2283 <tag><tt>loose_string_term</tt></tag>
2285 Accept single quotes as well as double quotes as terminators for string
2288 <tag><tt>missing_char_term</tt></tag>
2290 Accept single quoted character constants where the terminating quote is
2295 <bf/Note:/ This does not work in conjunction with <tt/.FEATURE
2296 loose_string_term/, since in this case the input would be ambiguous.
2298 <tag><tt>org_per_seg</tt><label id="org_per_seg"></tag>
2300 This feature makes relocatable/absolute mode local to the current segment.
2301 Using <tt><ref id=".ORG" name=".ORG"></tt> when <tt/org_per_seg/ is in
2302 effect will only enable absolute mode for the current segment. Dito for
2303 <tt><ref id=".RELOC" name=".RELOC"></tt>.
2305 <tag><tt>pc_assignment</tt></tag>
2307 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
2308 is enabled). Such an assignment is handled identical to the <tt><ref
2309 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
2310 removing the lines with the assignments may also be an option when porting
2311 code written for older assemblers).
2313 <tag><tt>ubiquitous_idents</tt></tag>
2315 Allow the use of instructions names as names for macros and symbols. This
2316 makes it possible to "overload" instructions by defining a macro with the
2317 same name. This does also make it possible to introduce hard to find errors
2318 in your code, so be careful!
2322 It is also possible to specify features on the command line using the
2323 <tt><ref id="option--feature" name="--feature"></tt> command line option.
2324 This is useful when translating sources written for older assemblers, when
2325 you don't want to change the source code.
2327 As an example, to translate sources written for Andre Fachats xa65
2328 assembler, the features
2331 labels_without_colons, pc_assignment, loose_char_term
2334 may be helpful. They do not make ca65 completely compatible, so you may not
2335 be able to translate the sources without changes, even when enabling these
2336 features. However, I have found several sources that translate without
2337 problems when enabling these features on the command line.
2340 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
2342 Insert an option string into the object file. There are two forms of
2343 this command, one specifies the option by a keyword, the second
2344 specifies it as a number. Since usage of the second one needs knowledge
2345 of the internal encoding, its use is not recommended and I will only
2346 describe the first form here.
2348 The command is followed by one of the keywords
2356 a comma and a string. The option is written into the object file
2357 together with the string value. This is currently unidirectional and
2358 there is no way to actually use these options once they are in the
2364 .fileopt comment, "Code stolen from my brother"
2365 .fileopt compiler, "BASIC 2.0"
2366 .fopt author, "J. R. User"
2370 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
2372 Import an absolute symbol from another module. The command is followed by a
2373 comma separated list of symbols to import. The command is similar to <tt>
2374 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
2375 written to the generated object file, even if the symbol is never referenced
2376 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
2377 references for unused symbols).
2382 .forceimport needthisone, needthistoo
2385 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2388 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
2390 Declare symbols as global. Must be followed by a comma separated list of
2391 symbols to declare. Symbols from the list, that are defined somewhere in the
2392 source, are exported, all others are imported. Additional <tt><ref
2393 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
2394 name=".EXPORT"></tt> commands for the same symbol are allowed.
2403 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
2405 Declare symbols as global. Must be followed by a comma separated list of
2406 symbols to declare. Symbols from the list, that are defined somewhere in the
2407 source, are exported, all others are imported. Additional <tt><ref
2408 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
2409 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
2410 in the list are explicitly marked as zero page symbols.
2419 <sect1><tt>.I16</tt><label id=".I16"><p>
2421 Valid only in 65816 mode. Switch the index registers to 16 bit.
2423 Note: This command will not emit any code, it will tell the assembler to
2424 create 16 bit operands for immediate operands.
2426 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
2427 name=".SMART"></tt> commands.
2430 <sect1><tt>.I8</tt><label id=".I8"><p>
2432 Valid only in 65816 mode. Switch the index registers to 8 bit.
2434 Note: This command will not emit any code, it will tell the assembler to
2435 create 8 bit operands for immediate operands.
2437 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
2438 name=".SMART"></tt> commands.
2441 <sect1><tt>.IF</tt><label id=".IF"><p>
2443 Conditional assembly: Evaluate an expression and switch assembler output
2444 on or off depending on the expression. The expression must be a constant
2445 expression, that is, all operands must be defined.
2447 A expression value of zero evaluates to FALSE, any other value evaluates
2451 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
2453 Conditional assembly: Check if there are any remaining tokens in this line,
2454 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
2455 condition is not true, further lines are not assembled until an <tt><ref
2456 id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2457 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2459 This command is often used to check if a macro parameter was given. Since an
2460 empty macro parameter will evaluate to nothing, the condition will evaluate
2461 to FALSE if an empty parameter was given.
2475 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2478 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
2480 Conditional assembly: Evaluate an expression and switch assembler output
2481 on or off depending on the constness of the expression.
2483 A const expression evaluates to to TRUE, a non const expression (one
2484 containing an imported or currently undefined symbol) evaluates to
2487 See also: <tt><ref id=".CONST" name=".CONST"></tt>
2490 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
2492 Conditional assembly: Check if a symbol is defined. Must be followed by
2493 a symbol name. The condition is true if the the given symbol is already
2494 defined, and false otherwise.
2496 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2499 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
2501 Conditional assembly: Check if there are any remaining tokens in this line,
2502 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
2503 condition is not true, further lines are not assembled until an <tt><ref
2504 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2505 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2507 This command is often used to check if a macro parameter was given.
2508 Since an empty macro parameter will evaluate to nothing, the condition
2509 will evaluate to FALSE if an empty parameter was given.
2522 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2525 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
2527 Conditional assembly: Check if a symbol is defined. Must be followed by
2528 a symbol name. The condition is true if the the given symbol is not
2529 defined, and false otherwise.
2531 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2534 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
2536 Conditional assembly: Check if a symbol is referenced. Must be followed
2537 by a symbol name. The condition is true if if the the given symbol was
2538 not referenced before, and false otherwise.
2540 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2543 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
2545 Conditional assembly: Check if the assembler is currently in 6502 mode
2546 (see <tt><ref id=".P02" name=".P02"></tt> command).
2549 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
2551 Conditional assembly: Check if the assembler is currently in 65816 mode
2552 (see <tt><ref id=".P816" name=".P816"></tt> command).
2555 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
2557 Conditional assembly: Check if the assembler is currently in 65C02 mode
2558 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
2561 <sect1><tt>.IFPSC02</tt><label id=".IFPSC02"><p>
2563 Conditional assembly: Check if the assembler is currently in 65SC02 mode
2564 (see <tt><ref id=".PSC02" name=".PSC02"></tt> command).
2567 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
2569 Conditional assembly: Check if a symbol is referenced. Must be followed
2570 by a symbol name. The condition is true if if the the given symbol was
2571 referenced before, and false otherwise.
2573 This command may be used to build subroutine libraries in include files
2574 (you may use separate object modules for this purpose too).
2579 .ifref ToHex ; If someone used this subroutine
2580 ToHex: tay ; Define subroutine
2586 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2589 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
2591 Import a symbol from another module. The command is followed by a comma
2592 separated list of symbols to import, with each one optionally followed by
2593 an address specification.
2599 .import bar: zeropage
2602 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
2605 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
2607 Import a symbol from another module. The command is followed by a comma
2608 separated list of symbols to import. The symbols are explicitly imported
2609 as zero page symbols (that is, symbols with values in byte range).
2617 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2620 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
2622 Include a file as binary data. The command expects a string argument
2623 that is the name of a file to include literally in the current segment.
2624 In addition to that, a start offset and a size value may be specified,
2625 separated by commas. If no size is specified, all of the file from the
2626 start offset to end-of-file is used. If no start position is specified
2627 either, zero is assumed (which means that the whole file is inserted).
2632 ; Include whole file
2633 .incbin "sprites.dat"
2635 ; Include file starting at offset 256
2636 .incbin "music.dat", $100
2638 ; Read 100 bytes starting at offset 200
2639 .incbin "graphics.dat", 200, 100
2643 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
2645 Include another file. Include files may be nested up to a depth of 16.
2654 <sect1><tt>.INTERRUPTOR</tt><label id=".INTERRUPTOR"><p>
2656 Export a symbol and mark it as an interruptor. This may be used together
2657 with the linker to build a table of interruptor subroutines that are called
2660 Note: The linker has a feature to build a table of marked routines, but it
2661 is your code that must call these routines, so just declaring a symbol as
2662 interruptor does nothing by itself.
2664 An interruptor is always exported as an absolute (16 bit) symbol. You don't
2665 need to use an additional <tt/.export/ statement, this is implied by
2666 <tt/.interruptor/. It may have an optional priority that is separated by a
2667 comma. Higher numeric values mean a higher priority. If no priority is
2668 given, the default priority of 7 is used. Be careful when assigning
2669 priorities to your own module constructors so they won't interfere with the
2670 ones in the cc65 library.
2675 .interruptor IrqHandler
2676 .interruptor Handler, 16
2679 See the <tt><ref id=".CONDES" name=".CONDES"></tt> command and the separate
2680 section <ref id="condes" name="Module constructors/destructors"> explaining
2681 the feature in more detail.
2684 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
2686 Switch on or off line continuations using the backslash character
2687 before a newline. The option is off by default.
2688 Note: Line continuations do not work in a comment. A backslash at the
2689 end of a comment is treated as part of the comment and does not trigger
2691 The command must be followed by a '+' or '-' character to switch the
2692 option on or off respectively.
2697 .linecont + ; Allow line continuations
2700 #$20 ; This is legal now
2704 <sect1><tt>.LIST</tt><label id=".LIST"><p>
2706 Enable output to the listing. The command must be followed by a boolean
2707 switch ("on", "off", "+" or "-") and will enable or disable listing
2709 The option has no effect if the listing is not enabled by the command line
2710 switch -l. If -l is used, an internal counter is set to 1. Lines are output
2711 to the listing file, if the counter is greater than zero, and suppressed if
2712 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
2718 .list on ; Enable listing output
2722 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
2724 Set, how many bytes are shown in the listing for one source line. The
2725 default is 12, so the listing will show only the first 12 bytes for any
2726 source line that generates more than 12 bytes of code or data.
2727 The directive needs an argument, which is either "unlimited", or an
2728 integer constant in the range 4..255.
2733 .listbytes unlimited ; List all bytes
2734 .listbytes 12 ; List the first 12 bytes
2735 .incbin "data.bin" ; Include large binary file
2739 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
2741 This command may only be used inside a macro definition. It declares a
2742 list of identifiers as local to the macro expansion.
2744 A problem when using macros are labels: Since they don't change their name,
2745 you get a "duplicate symbol" error if the macro is expanded the second time.
2746 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
2747 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
2750 Some other assemblers start a new lexical block inside a macro expansion.
2751 This has some drawbacks however, since that will not allow <em/any/ symbol
2752 to be visible outside a macro, a feature that is sometimes useful. The
2753 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
2754 to address the problem.
2756 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
2760 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
2762 Defines the character that start "cheap" local labels. You may use one
2763 of '@' and '?' as start character. The default is '@'.
2765 Cheap local labels are labels that are visible only between two non
2766 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
2767 using explicit lexical nesting.
2774 Clear: lda #$00 ; Global label
2775 ?Loop: sta Mem,y ; Local label
2779 Sub: ... ; New global label
2780 bne ?Loop ; ERROR: Unknown identifier!
2784 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
2786 Insert a predefined macro package. The command is followed by an
2787 identifier specifying the macro package to insert. Available macro
2791 atari Defines the scrcode macro.
2792 cbm Defines the scrcode macro.
2793 cpu Defines constants for the .CPU variable.
2794 generic Defines generic macros like add and sub.
2795 longbranch Defines conditional long jump macros.
2798 Including a macro package twice, or including a macro package that
2799 redefines already existing macros will lead to an error.
2804 .macpack longbranch ; Include macro package
2806 cmp #$20 ; Set condition codes
2807 jne Label ; Jump long on condition
2810 Macro packages are explained in more detail in section <ref
2811 id="macropackages" name="Macro packages">.
2814 <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"><p>
2816 Start a classic macro definition. The command is followed by an identifier
2817 (the macro name) and optionally by a comma separated list of identifiers
2818 that are macro parameters.
2820 See section <ref id="macros" name="Macros">.
2823 <sect1><tt>.ORG</tt><label id=".ORG"><p>
2825 Start a section of absolute code. The command is followed by a constant
2826 expression that gives the new PC counter location for which the code is
2827 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
2830 By default, absolute/relocatable mode is global (valid even when switching
2831 segments). Using <tt>.FEATURE <ref id="org_per_seg" name="org_per_seg"></tt>
2832 it can be made segment local.
2834 Please note that you <em/do not need/ <tt/.ORG/ in most cases. Placing
2835 code at a specific address is the job of the linker, not the assembler, so
2836 there is usually no reason to assemble code to a specific address.
2841 .org $7FF ; Emit code starting at $7FF
2845 <sect1><tt>.OUT</tt><label id=".OUT"><p>
2847 Output a string to the console without producing an error. This command
2848 is similar to <tt/.ERROR/, however, it does not force an assembler error
2849 that prevents the creation of an object file.
2854 .out "This code was written by the codebuster(tm)"
2857 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
2858 id=".ERROR" name=".ERROR"></tt> directives.
2861 <sect1><tt>.P02</tt><label id=".P02"><p>
2863 Enable the 6502 instruction set, disable 65SC02, 65C02 and 65816
2864 instructions. This is the default if not overridden by the
2865 <tt><ref id="option--cpu" name="--cpu"></tt> command line option.
2867 See: <tt><ref id=".PC02" name=".PC02"></tt>, <tt><ref id=".PSC02"
2868 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2871 <sect1><tt>.P816</tt><label id=".P816"><p>
2873 Enable the 65816 instruction set. This is a superset of the 65SC02 and
2874 6502 instruction sets.
2876 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
2877 name=".PSC02"></tt> and <tt><ref id=".PC02" name=".PC02"></tt>
2880 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
2882 Set the page length for the listing. Must be followed by an integer
2883 constant. The value may be "unlimited", or in the range 32 to 127. The
2884 statement has no effect if no listing is generated. The default value is -1
2885 (unlimited) but may be overridden by the <tt/--pagelength/ command line
2886 option. Beware: Since ca65 is a one pass assembler, the listing is generated
2887 after assembly is complete, you cannot use multiple line lengths with one
2888 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
2893 .pagelength 66 ; Use 66 lines per listing page
2895 .pagelength unlimited ; Unlimited page length
2899 <sect1><tt>.PC02</tt><label id=".PC02"><p>
2901 Enable the 65C02 instructions set. This instruction set includes all
2902 6502 and 65SC02 instructions.
2904 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
2905 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2908 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
2910 Pop the last pushed segment from the stack, and set it.
2912 This command will switch back to the segment that was last pushed onto the
2913 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
2914 command, and remove this entry from the stack.
2916 The assembler will print an error message if the segment stack is empty
2917 when this command is issued.
2919 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
2922 <sect1><tt>.PROC</tt><label id=".PROC"><p>
2924 Start a nested lexical level with the given name and adds a symbol with this
2925 name to the enclosing scope. All new symbols from now on are in the local
2926 lexical level and are accessible from outside only via <ref id="scopesyntax"
2927 name="explicit scope specification">. Symbols defined outside this local
2928 level may be accessed as long as their names are not used for new symbols
2929 inside the level. Symbols names in other lexical levels do not clash, so you
2930 may use the same names for identifiers. The lexical level ends when the
2931 <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read. Lexical levels
2932 may be nested up to a depth of 16 (this is an artificial limit to protect
2933 against errors in the source).
2935 Note: Macro names are always in the global level and in a separate name
2936 space. There is no special reason for this, it's just that I've never
2937 had any need for local macro definitions.
2942 .proc Clear ; Define Clear subroutine, start new level
2944 L1: sta Mem,y ; L1 is local and does not cause a
2945 ; duplicate symbol error if used in other
2948 bne L1 ; Reference local symbol
2950 .endproc ; Leave lexical level
2953 See: <tt/<ref id=".ENDPROC" name=".ENDPROC">/ and <tt/<ref id=".SCOPE"
2957 <sect1><tt>.PSC02</tt><label id=".PSC02"><p>
2959 Enable the 65SC02 instructions set. This instruction set includes all
2962 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PC02"
2963 name=".PC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2966 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
2968 Push the currently active segment onto a stack. The entries on the stack
2969 include the name of the segment and the segment type. The stack has a size
2972 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
2973 to switch to another segment and to restore the old segment later, without
2974 even knowing the name and type of the current segment.
2976 The assembler will print an error message if the segment stack is already
2977 full, when this command is issued.
2979 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
2982 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
2984 Switch back to relocatable mode. See the <tt><ref id=".ORG"
2985 name=".ORG"></tt> command.
2988 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
2990 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
2991 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
2992 a constant expression that tells how many times the commands in the body
2993 should get repeated. Optionally, a comma and an identifier may be specified.
2994 If this identifier is found in the body of the repeat statement, it is
2995 replaced by the current repeat count (starting with zero for the first time
2996 the body is repeated).
2998 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
2999 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
3000 level will be used, not the one from the outer level.
3004 The following macro will emit a string that is "encrypted" in that all
3005 characters of the string are XORed by the value $55.
3009 .repeat .strlen(Arg), I
3010 .byte .strat(Arg, I) ^ $55
3015 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
3018 <sect1><tt>.RES</tt><label id=".RES"><p>
3020 Reserve storage. The command is followed by one or two constant
3021 expressions. The first one is mandatory and defines, how many bytes of
3022 storage should be defined. The second, optional expression must by a
3023 constant byte value that will be used as value of the data. If there
3024 is no fill value given, the linker will use the value defined in the
3025 linker configuration file (default: zero).
3030 ; Reserve 12 bytes of memory with value $AA
3035 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
3037 Switch to the RODATA segment. The name of the RODATA segment is always
3038 "RODATA", so this is a shortcut for
3044 The RODATA segment is a segment that is used by the compiler for
3045 readonly data like string constants.
3047 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
3050 <sect1><tt>.SCOPE</tt><label id=".SCOPE"><p>
3052 Start a nested lexical level with the given name. All new symbols from now
3053 on are in the local lexical level and are accessible from outside only via
3054 <ref id="scopesyntax" name="explicit scope specification">. Symbols defined
3055 outside this local level may be accessed as long as their names are not used
3056 for new symbols inside the level. Symbols names in other lexical levels do
3057 not clash, so you may use the same names for identifiers. The lexical level
3058 ends when the <tt><ref id=".ENDSCOPE" name=".ENDSCOPE"></tt> command is
3059 read. Lexical levels may be nested up to a depth of 16 (this is an
3060 artificial limit to protect against errors in the source).
3062 Note: Macro names are always in the global level and in a separate name
3063 space. There is no special reason for this, it's just that I've never
3064 had any need for local macro definitions.
3069 .scope Error ; Start new scope named Error
3071 File = 1 ; File error
3072 Parse = 2 ; Parse error
3073 .endscope ; Close lexical level
3076 lda #Error::File ; Use symbol from scope Error
3079 See: <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/ and <tt/<ref id=".PROC"
3083 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
3085 Switch to another segment. Code and data is always emitted into a
3086 segment, that is, a named section of data. The default segment is
3087 "CODE". There may be up to 254 different segments per object file
3088 (and up to 65534 per executable). There are shortcut commands for
3089 the most common segments ("CODE", "DATA" and "BSS").
3091 The command is followed by a string containing the segment name (there are
3092 some constraints for the name - as a rule of thumb use only those segment
3093 names that would also be valid identifiers). There may also be an optional
3094 address size separated by a colon. See the section covering <tt/<ref
3095 id="address-sizes" name="address sizes">/ for more information.
3097 The default address size for a segment depends on the memory model specified
3098 on the command line. The default is "absolute", which means that you don't
3099 have to use an address size modifier in most cases.
3101 "absolute" means that the is a segment with 16 bit (absolute) addressing.
3102 That is, the segment will reside somewhere in core memory outside the zero
3103 page. "zeropage" (8 bit) means that the segment will be placed in the zero
3104 page and direct (short) addressing is possible for data in this segment.
3106 Beware: Only labels in a segment with the zeropage attribute are marked
3107 as reachable by short addressing. The `*' (PC counter) operator will
3108 work as in other segments and will create absolute variable values.
3110 Please note that a segment cannot have two different address sizes. A
3111 segment specified as zeropage cannot be declared as being absolute later.
3116 .segment "ROM2" ; Switch to ROM2 segment
3117 .segment "ZP2": zeropage ; New direct segment
3118 .segment "ZP2" ; Ok, will use last attribute
3119 .segment "ZP2": absolute ; Error, redecl mismatch
3122 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
3123 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref
3124 id=".RODATA" name=".RODATA"></tt>
3127 <sect1><tt>.SETCPU</tt><label id=".SETCPU"><p>
3129 Switch the CPU instruction set. The command is followed by a string that
3130 specifies the CPU. Possible values are those that can also be supplied to
3131 the <tt><ref id="option--cpu" name="--cpu"></tt> command line option,
3132 namely: 6502, 6502X, 65SC02, 65C02, 65816, sunplus and HuC6280. Please
3133 note that support for the sunplus CPU is not available in the freeware
3134 version, because the instruction set of the sunplus CPU is "proprietary
3137 See: <tt><ref id=".CPU" name=".CPU"></tt>,
3138 <tt><ref id=".IFP02" name=".IFP02"></tt>,
3139 <tt><ref id=".IFP816" name=".IFP816"></tt>,
3140 <tt><ref id=".IFPC02" name=".IFPC02"></tt>,
3141 <tt><ref id=".IFPSC02" name=".IFPSC02"></tt>,
3142 <tt><ref id=".P02" name=".P02"></tt>,
3143 <tt><ref id=".P816" name=".P816"></tt>,
3144 <tt><ref id=".PC02" name=".PC02"></tt>,
3145 <tt><ref id=".PSC02" name=".PSC02"></tt>
3148 <sect1><tt>.SMART</tt><label id=".SMART"><p>
3150 Switch on or off smart mode. The command must be followed by a '+' or '-'
3151 character to switch the option on or off respectively. The default is off
3152 (that is, the assembler doesn't try to be smart), but this default may be
3153 changed by the -s switch on the command line.
3155 In smart mode the assembler will do the following:
3158 <item>Track usage of the <tt/REP/ and <tt/SEP/ instructions in 65816 mode
3159 and update the operand sizes accordingly. If the operand of such an
3160 instruction cannot be evaluated by the assembler (for example, because
3161 the operand is an imported symbol), a warning is issued. Beware: Since
3162 the assembler cannot trace the execution flow this may lead to false
3163 results in some cases. If in doubt, use the <tt/.Inn/ and <tt/.Ann/
3164 instructions to tell the assembler about the current settings.
3165 <item>In 65816 mode, replace a <tt/RTS/ instruction by <tt/RTL/ if it is
3166 used within a procedure declared as <tt/far/, or if the procedure has
3167 no explicit address specification, but it is <tt/far/ because of the
3175 .smart - ; Stop being smart
3178 See: <tt><ref id=".A16" name=".A16"></tt>,
3179 <tt><ref id=".A8" name=".A8"></tt>,
3180 <tt><ref id=".I16" name=".I16"></tt>,
3181 <tt><ref id=".I8" name=".I8"></tt>
3184 <sect1><tt>.STRUCT</tt><label id=".STRUCT"><p>
3186 Starts a struct definition. Structs are covered in a separate section named
3187 <ref id="structs" name=""Structs and unions"">.
3189 See: <tt><ref id=".ENDSTRUCT" name=".ENDSTRUCT"></tt>
3192 <sect1><tt>.SUNPLUS</tt><label id=".SUNPLUS"><p>
3194 Enable the SunPlus instructions set. This command will not work in the
3195 freeware version of the assembler, because the instruction set is
3196 "proprietary and confidential".
3198 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3199 name=".PSC02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt>, and
3200 <tt><ref id=".P816" name=".P816"></tt>
3203 <sect1><tt>.TAG</tt><label id=".TAG"><p>
3205 Allocate space for a struct or union.
3216 .tag Point ; Allocate 4 bytes
3220 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
3222 Force an assembly warning. The assembler will output a warning message
3223 preceded by "User warning". This warning will always be output, even if
3224 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
3225 command line option.
3227 This command may be used to output possible problems when assembling
3236 .warning "Forward jump in jne, cannot optimize!"
3246 See also the <tt><ref id=".ERROR" name=".ERROR"></tt> and <tt><ref id=".OUT"
3247 name=".OUT"></tt> directives.
3250 <sect1><tt>.WORD</tt><label id=".WORD"><p>
3252 Define word sized data. Must be followed by a sequence of (word ranged,
3253 but not necessarily constant) expressions.
3258 .word $0D00, $AF13, _Clear
3262 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
3264 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
3265 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
3269 .segment "ZEROPAGE", zeropage
3272 Because of the "zeropage" attribute, labels declared in this segment are
3273 addressed using direct addressing mode if possible. You <em/must/ instruct
3274 the linker to place this segment somewhere in the address range 0..$FF
3275 otherwise you will get errors.
3277 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
3281 <sect>Macros<label id="macros"><p>
3284 <sect1>Introduction<p>
3286 Macros may be thought of as "parametrized super instructions". Macros are
3287 sequences of tokens that have a name. If that name is used in the source
3288 file, the macro is "expanded", that is, it is replaced by the tokens that
3289 were specified when the macro was defined.
3292 <sect1>Macros without parameters<p>
3294 In it's simplest form, a macro does not have parameters. Here's an
3298 .macro asr ; Arithmetic shift right
3299 cmp #$80 ; Put bit 7 into carry
3300 ror ; Rotate right with carry
3304 The macro above consists of two real instructions, that are inserted into
3305 the code, whenever the macro is expanded. Macro expansion is simply done
3306 by using the name, like this:
3315 <sect1>Parametrized macros<p>
3317 When using macro parameters, macros can be even more useful:
3331 When calling the macro, you may give a parameter, and each occurrence of
3332 the name "addr" in the macro definition will be replaced by the given
3351 A macro may have more than one parameter, in this case, the parameters
3352 are separated by commas. You are free to give less parameters than the
3353 macro actually takes in the definition. You may also leave intermediate
3354 parameters empty. Empty parameters are replaced by empty space (that is,
3355 they are removed when the macro is expanded). If you have a look at our
3356 macro definition above, you will see, that replacing the "addr" parameter
3357 by nothing will lead to wrong code in most lines. To help you, writing
3358 macros with a variable parameter list, there are some control commands:
3360 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
3361 returns true, if there are any tokens on the remainder of the line. Since
3362 empty parameters are replaced by nothing, this may be used to test if a given
3363 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
3366 Look at this example:
3369 .macro ldaxy a, x, y
3382 This macro may be called as follows:
3385 ldaxy 1, 2, 3 ; Load all three registers
3387 ldaxy 1, , 3 ; Load only a and y
3389 ldaxy , , 3 ; Load y only
3392 There's another helper command for determining, which macro parameters are
3393 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is
3394 replaced by the parameter count given, <em/including/ intermediate empty macro
3398 ldaxy 1 ; .PARAMCOUNT = 1
3399 ldaxy 1,,3 ; .PARAMCOUNT = 3
3400 ldaxy 1,2 ; .PARAMCOUNT = 2
3401 ldaxy 1, ; .PARAMCOUNT = 2
3402 ldaxy 1,2,3 ; .PARAMCOUNT = 3
3405 Macro parameters may optionally be enclosed into curly braces. This allows the
3406 inclusion of tokens that would otherwise terminate the parameter (the comma in
3407 case of a macro parameter).
3410 .macro foo arg1, arg2
3414 foo ($00,x) ; Two parameters passed
3415 foo {($00,x)} ; One parameter passed
3418 In the first case, the macro is called with two parameters: '<tt/($00/'
3419 and 'x)'. The comma is not passed to the macro, since it is part of the
3420 calling sequence, not the parameters.
3422 In the second case, '($00,x)' is passed to the macro, this time
3423 including the comma.
3426 <sect1>Detecting parameter types<p>
3428 Sometimes it is nice to write a macro that acts differently depending on the
3429 type of the argument supplied. An example would be a macro that loads a 16 bit
3430 value from either an immediate operand, or from memory. The <tt/<ref
3431 id=".MATCH" name=".MATCH">/ and <tt/<ref id=".XMATCH" name=".XMATCH">/
3432 functions will allow you to do exactly this:
3436 .if (.match (.left (1, {arg}), #))
3438 lda #<(.right (.tcount ({arg})-1, {arg}))
3439 ldx #>(.right (.tcount ({arg})-1, {arg}))
3441 ; assume absolute or zero page
3448 Using the <tt/<ref id=".MATCH" name=".MATCH">/ function, the macro is able to
3449 check if its argument begins with a hash mark. If so, two immediate loads are
3450 emitted, Otherwise a load from an absolute zero page memory location is
3451 assumed. Please note how the curly braces are used to enclose parameters to
3452 pseudo functions handling token lists. This is necessary, because the token
3453 lists may include commas or parens, which would be treated by the assembler
3456 The macro can be used as
3461 ldax #$1234 ; X=$12, A=$34
3463 ldax foo ; X=$56, A=$78
3467 <sect1>Recursive macros<p>
3469 Macros may be used recursively:
3472 .macro push r1, r2, r3
3481 There's also a special macro to help writing recursive macros: <tt><ref
3482 id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion
3486 .macro push r1, r2, r3, r4, r5, r6, r7
3488 ; First parameter is empty
3494 push r2, r3, r4, r5, r6, r7
3498 When expanding this macro, the expansion will push all given parameters
3499 until an empty one is encountered. The macro may be called like this:
3502 push $20, $21, $32 ; Push 3 ZP locations
3503 push $21 ; Push one ZP location
3507 <sect1>Local symbols inside macros<p>
3509 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
3510 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
3511 Have a look at the inc16 macro above. Here is it again:
3525 If you have a closer look at the code, you will notice, that it could be
3526 written more efficiently, like this:
3537 But imagine what happens, if you use this macro twice? Since the label
3538 "Skip" has the same name both times, you get a "duplicate symbol" error.
3539 Without a way to circumvent this problem, macros are not as useful, as
3540 they could be. One solution is, to start a new lexical block inside the
3554 Now the label is local to the block and not visible outside. However,
3555 sometimes you want a label inside the macro to be visible outside. To make
3556 that possible, there's a new command that's only usable inside a macro
3557 definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one
3558 or more symbols as local to the macro expansion. The names of local variables
3559 are replaced by a unique name in each separate macro expansion. So we could
3560 also solve the problem above by using <tt/.LOCAL/:
3564 .local Skip ; Make Skip a local symbol
3571 Skip: ; Not visible outside
3576 <sect1>C style macros<p>
3578 Starting with version 2.5 of the assembler, there is a second macro type
3579 available: C style macros using the <tt/.DEFINE/ directive. These macros are
3580 similar to the classic macro type described above, but behaviour is sometimes
3585 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
3586 span more than a line. You may use line continuation (see <tt><ref
3587 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
3588 more than one line for increased readability, but the macro itself
3589 may not contain an end-of-line token.
3591 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
3592 the name space with classic macros, but they are detected and replaced
3593 at the scanner level. While classic macros may be used in every place,
3594 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
3595 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
3596 they are more versatile in some situations.
3598 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
3599 parameters. While classic macros may have empty parameters, this is
3600 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
3601 For this macro type, the number of actual parameters must match
3602 exactly the number of formal parameters.
3604 To make this possible, formal parameters are enclosed in braces when
3605 defining the macro. If there are no parameters, the empty braces may
3608 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
3609 contain end-of-line tokens, there are things that cannot be done. They
3610 may not contain several processor instructions for example. So, while
3611 some things may be done with both macro types, each type has special
3612 usages. The types complement each other.
3616 Let's look at a few examples to make the advantages and disadvantages
3619 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
3620 following <tt/.DEFINE/:
3625 foo EQU $1234 ; This is accepted now
3628 You may use the directive to define string constants used elsewhere:
3631 ; Define the version number
3632 .define VERSION "12.3a"
3638 Macros with parameters may also be useful:
3641 .define DEBUG(message) .out message
3643 DEBUG "Assembling include file #3"
3646 Note that, while formal parameters have to be placed in braces, this is
3647 not true for the actual parameters. Beware: Since the assembler cannot
3648 detect the end of one parameter, only the first token is used. If you
3649 don't like that, use classic macros instead:
3657 (This is an example where a problem can be solved with both macro types).
3660 <sect1>Characters in macros<p>
3662 When using the <ref id="option-t" name="-t"> option, characters are translated
3663 into the target character set of the specific machine. However, this happens
3664 as late as possible. This means that strings are translated if they are part
3665 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
3666 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
3667 used as part of an expression.
3669 This behaviour is very intuitive outside of macros but may be confusing when
3670 doing more complex macros. If you compare characters against numeric values,
3671 be sure to take the translation into account.
3676 <sect>Macro packages<label id="macropackages"><p>
3678 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
3679 macro packages may be included with just one command. Available macro packages
3683 <sect1><tt>.MACPACK generic</tt><p>
3685 This macro package defines macros that are useful in almost any program.
3686 Currently, two macros are defined:
3701 <sect1><tt>.MACPACK longbranch</tt><p>
3703 This macro package defines long conditional jumps. They are named like the
3704 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
3705 definition for the "<tt/jeq/" macro, the other macros are built using the same
3710 .if .def(Target) .and ((*+2)-(Target) <= 127)
3719 All macros expand to a short branch, if the label is already defined (back
3720 jump) and is reachable with a short jump. Otherwise the macro expands to a
3721 conditional branch with the branch condition inverted, followed by an absolute
3722 jump to the actual branch target.
3724 The package defines the following macros:
3727 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
3732 <sect1><tt>.MACPACK cbm</tt><p>
3734 The cbm macro package will define a macro named <tt/scrcode/. It takes a
3735 string as argument and places this string into memory translated into screen
3739 <sect1><tt>.MACPACK cpu</tt><p>
3741 This macro package does not define any macros but constants used to examine
3742 the value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable. For
3743 each supported CPU a constant similar to
3755 is defined. These constants may be used to determine the exact type of the
3756 currently enabled CPU. In addition to that, for each CPU instruction set,
3757 another constant is defined:
3769 The value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable may
3770 be checked with <tt/<ref id="operators" name=".BITAND">/ to determine if the
3771 currently enabled CPU supports a specific instruction set. For example the
3772 65C02 supports all instructions of the 65SC02 CPU, so it has the
3773 <tt/CPU_ISET_65SC02/ bit set in addition to its native <tt/CPU_ISET_65C02/
3777 .if (.cpu .bitand CPU_ISET_65SC02)
3785 it is possible to determine if the
3791 instruction is supported, which is the case for the 65SC02, 65C02 and 65816
3792 CPUs (the latter two are upwards compatible to the 65SC02).
3796 <sect>Predefined constants<label id="predefined-constants"><p>
3798 For better orthogonality, the assembler defines similar symbols as the
3799 compiler, depending on the target system selected:
3802 <item><tt/__ACE__/ - Target system is <tt/ace/
3803 <item><tt/__APPLE2__/ - Target system is <tt/apple2/
3804 <item><tt/__APPLE2ENH__/ - Target system is <tt/apple2enh/
3805 <item><tt/__ATARI__/ - Target system is <tt/atari/
3806 <item><tt/__ATMOS__/ - Target system is <tt/atmos/
3807 <item><tt/__BBC__/ - Target system is <tt/bbc/
3808 <item><tt/__C128__/ - Target system is <tt/c128/
3809 <item><tt/__C16__/ - Target system is <tt/c16/
3810 <item><tt/__C64__/ - Target system is <tt/c64/
3811 <item><tt/__CBM__/ - Target is a Commodore system
3812 <item><tt/__CBM510__/ - Target system is <tt/cbm510/
3813 <item><tt/__CBM610__/ - Target system is <tt/cbm610/
3814 <item><tt/__GEOS__/ - Target system is <tt/geos/
3815 <item><tt/__LUNIX__/ - Target system is <tt/lunix/
3816 <item><tt/__NES__/ - Target system is <tt/nes/
3817 <item><tt/__PET__/ - Target system is <tt/pet/
3818 <item><tt/__PLUS4__/ - Target system is <tt/plus4/
3819 <item><tt/__SUPERVISION__/ - Target system is <tt/supervision/
3820 <item><tt/__VIC20__/ - Target system is <tt/vic20/
3824 <sect>Structs and unions<label id="structs"><p>
3828 Structs and unions are special forms of <ref id="scopes" name="scopes">. They
3829 are to some degree comparable to their C counterparts. Both have a list of
3830 members. Each member allocates storage and may optionally have a name, which,
3831 in case of a struct, is the offset from the beginning and, in case of a union,
3835 <sect1>Declaration<p>
3837 Here is an example for a very simple struct with two members and a total size
3847 A union shares the total space between all its members, its size is the same
3848 as that of the largest member.
3850 A struct or union must not necessarily have a name. If it is anonymous, no
3851 local scope is opened, the identifiers used to name the members are placed
3852 into the current scope instead.
3854 A struct may contain unnamed members and definitions of local structs. The
3855 storage allocators may contain a multiplier, as in the example below:
3860 .word 2 ; Allocate two words
3867 <sect1>The <tt/.TAG/ keyword<p>
3869 Using the <ref id=".TAG" name=".TAG"> keyword, it is possible to reserve space
3870 for an already defined struct or unions within another struct:
3884 Space for a struct or union may be allocated using the <ref id=".TAG"
3885 name=".TAG"> directive.
3891 Currently, members are just offsets from the start of the struct or union. To
3892 access a field of a struct, the member offset has to be added to the address
3893 of the struct itself:
3896 lda C+Circle::Radius ; Load circle radius into A
3899 This may change in a future version of the assembler.
3902 <sect1>Limitations<p>
3904 Structs and unions are currently implemented as nested symbol tables (in fact,
3905 they were a by-product of the improved scoping rules). Currently, the
3906 assembler has no idea of types. This means that the <ref id=".TAG"
3907 name=".TAG"> keyword will only allocate space. You won't be able to initialize
3908 variables declared with <ref id=".TAG" name=".TAG">, and adding an embedded
3909 structure to another structure with <ref id=".TAG" name=".TAG"> will not make
3910 this structure accessible by using the '::' operator.
3914 <sect>Module constructors/destructors<label id="condes"><p>
3916 <em>Note:</em> This section applies mostly to C programs, so the explanation
3917 below uses examples from the C libraries. However, the feature may also be
3918 useful for assembler programs.
3923 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
3924 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
3925 name=".INTERRUPTOR"></tt> keywords it it possible to export functions in a
3926 special way. The linker is able to generate tables with all functions of a
3927 specific type. Such a table will <em>only</em> include symbols from object
3928 files that are linked into a specific executable. This may be used to add
3929 initialization and cleanup code for library modules, or a table of interrupt
3932 The C heap functions are an example where module initialization code is used.
3933 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
3934 variables that contain the start and the end of the heap, pointers to the free
3935 list and so on. Since the end of the heap depends on the size and start of the
3936 stack, it must be initialized at runtime. However, initializing these
3937 variables for programs that do not use the heap are a waste of time and
3940 So the central module defines a function that contains initialization code and
3941 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
3942 this module is added to an executable by the linker, the initialization
3943 function will be placed into the table of constructors by the linker. The C
3944 startup code will call all constructors before <tt/main/ and all destructors
3945 after <tt/main/, so without any further work, the heap initialization code is
3946 called once the module is linked in.
3948 While it would be possible to add explicit calls to initialization functions
3949 in the startup code, the new approach has several advantages:
3953 If a module is not included, the initialization code is not linked in and not
3954 called. So you don't pay for things you don't need.
3957 Adding another library that needs initialization does not mean that the
3958 startup code has to be changed. Before we had module constructors and
3959 destructors, the startup code for all systems had to be adjusted to call the
3960 new initialization code.
3963 The feature saves memory: Each additional initialization function needs just
3964 two bytes in the table (a pointer to the function).
3969 <sect1>Calling order<p>
3971 The symbols are sorted in increasing priority order by the linker when using
3972 one of the builtin linker configurations, so the functions with lower
3973 priorities come first and are followed by those with higher priorities. The C
3974 library runtime subroutine that walks over the function tables calls the
3975 functions starting from the top of the table - which means that functions with
3976 a high priority are called first.
3978 So when using the C runtime, functions are called with high priority functions
3979 first, followed by low priority functions.
3984 When using these special symbols, please take care of the following:
3989 The linker will only generate function tables, it will not generate code to
3990 call these functions. If you're using the feature in some other than the
3991 existing C environments, you have to write code to call all functions in a
3992 linker generated table yourself. See the <tt/condes/ and <tt/callirq/ modules
3993 in the C runtime for an example on how to do this.
3996 The linker will only add addresses of functions that are in modules linked to
3997 the executable. This means that you have to be careful where to place the
3998 condes functions. If initialization or an irq handler is needed for a group of
3999 functions, be sure to place the function into a module that is linked in
4000 regardless of which function is called by the user.
4003 The linker will generate the tables only when requested to do so by the
4004 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
4005 be requested separately.
4008 Constructors and destructors may have priorities. These priorities determine
4009 the order of the functions in the table. If your initialization or cleanup code
4010 does depend on other initialization or cleanup code, you have to choose the
4011 priority for the functions accordingly.
4014 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
4015 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
4016 name=".INTERRUPTOR"></tt> statements, there is also a more generic command:
4017 <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to specify an
4018 additional type. Predefined types are 0 (constructor), 1 (destructor) and 2
4019 (interruptor). The linker generates a separate table for each type on request.
4024 <sect>Porting sources from other assemblers<p>
4026 Sometimes it is necessary to port code written for older assemblers to ca65.
4027 In some cases, this can be done without any changes to the source code by
4028 using the emulation features of ca65 (see <tt><ref id=".FEATURE"
4029 name=".FEATURE"></tt>). In other cases, it is necessary to make changes to the
4032 Probably the biggest difference is the handling of the <tt><ref id=".ORG"
4033 name=".ORG"></tt> directive. ca65 generates relocatable code, and placement is
4034 done by the linker. Most other assemblers generate absolute code, placement is
4035 done within the assembler and there is no external linker.
4037 In general it is not a good idea to write new code using the emulation
4038 features of the assembler, but there may be situations where even this rule is
4043 You need to use some of the ca65 emulation features to simulate the behaviour
4044 of such simple assemblers.
4047 <item>Prepare your sourcecode like this:
4050 ; if you want TASS style labels without colons
4051 .feature labels_without_colons
4053 ; if you want TASS style character constants
4054 ; ("a" instead of the default 'a')
4055 .feature loose_char_term
4057 .word *+2 ; the cbm load address
4062 notice that the two emulation features are mostly useful for porting
4063 sources originally written in/for TASS, they are not needed for the
4064 actual "simple assembler operation" and are not recommended if you are
4065 writing new code from scratch.
4067 <item>Replace all program counter assignments (which are not possible in ca65
4068 by default, and the respective emulation feature works different from what
4069 you'd expect) by another way to skip to memory locations, for example the
4070 <tt><ref id=".RES" name=".RES"></tt> directive.
4074 .res $2000-* ; reserve memory up to $2000
4077 Please note that other than the original TASS, ca65 can never move the program
4078 counter backwards - think of it as if you are assembling to disk with TASS.
4080 <item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.goto/ etc.) must be
4081 rewritten to match ca65 syntax. Most importantly notice that due to the lack
4082 of <tt/.goto/, everything involving loops must be replaced by
4083 <tt><ref id=".REPEAT" name=".REPEAT"></tt>.
4085 <item>To assemble code to a different address than it is executed at, use the
4086 <tt><ref id=".ORG" name=".ORG"></tt> directive instead of
4087 <tt/.offs/-constructs.
4094 .reloc ; back to normal
4097 <item>Then assemble like this:
4100 cl65 --start-addr 0x0ffe -t none myprog.s -o myprog.prg
4103 Note that you need to use the actual start address minus two, since two bytes
4104 are used for the cbm load address.
4109 <sect>Bugs/Feedback<p>
4111 If you have problems using the assembler, if you find any bugs, or if
4112 you're doing something interesting with the assembler, I would be glad to
4113 hear from you. Feel free to contact me by email
4114 (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
4120 ca65 (and all cc65 binutils) are (C) Copyright 1998-2003 Ullrich von
4121 Bassewitz. For usage of the binaries and/or sources the following
4122 conditions do apply:
4124 This software is provided 'as-is', without any expressed or implied
4125 warranty. In no event will the authors be held liable for any damages
4126 arising from the use of this software.
4128 Permission is granted to anyone to use this software for any purpose,
4129 including commercial applications, and to alter it and redistribute it
4130 freely, subject to the following restrictions:
4133 <item> The origin of this software must not be misrepresented; you must not
4134 claim that you wrote the original software. If you use this software
4135 in a product, an acknowledgment in the product documentation would be
4136 appreciated but is not required.
4137 <item> Altered source versions must be plainly marked as such, and must not
4138 be misrepresented as being the original software.
4139 <item> This notice may not be removed or altered from any source