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>19.07.2000, 29.11.2000, 02.10.2001
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 -o name Name the output file
101 -t sys Set the target system
102 -v Increase verbosity
105 --auto-import Mark unresolved symbols as import
106 --cpu type Set cpu type
107 --debug-info Add debug info to object file
108 --feature name Set an emulation feature
109 --help Help (this text)
110 --ignore-case Ignore case of symbols
111 --include-dir dir Set an include directory search path
112 --list-bytes n Maximum number of bytes per listing line
113 --listing Create a listing if assembly was ok
114 --pagelength n Set the page length for the listing
115 --smart Enable smart mode
116 --target sys Set the target system
117 --verbose Increase verbosity
118 --version Print the assembler version
119 ---------------------------------------------------------------------------
123 <sect1>Command line options in detail<p>
125 Here is a description of all the command line options:
129 <label id="option--cpu">
130 <tag><tt>--cpu type</tt></tag>
132 Set the default for the CPU type. The option takes a parameter, which
135 6502, 65SC02, 65C02, 65816, sunplus, sweet16
137 The sunplus cpu is not available in the freeware version, because the
138 instruction set is "proprietary and confidential".
141 <label id="option--feature">
142 <tag><tt>--feature name</tt></tag>
144 Enable an emulation feature. This is identical as using <tt/.FEATURE/
145 in the source with two exceptions: Feature names must be lower case, and
146 each feature must be specified by using an extra <tt/--feature/ option,
147 comma separated lists are not allowed.
149 See the discussion of the <tt><ref id=".FEATURE" name=".FEATURE"></tt>
150 command for a list of emulation features.
153 <label id="option-g">
154 <tag><tt>-g, --debug-info</tt></tag>
156 When this option (or the equivalent control command <tt/.DEBUGINFO/) is
157 used, the assembler will add a section to the object file that contains
158 all symbols (including local ones) together with the symbol values and
159 source file positions. The linker will put these additional symbols into
160 the VICE label file, so even local symbols can be seen in the VICE
164 <tag><tt>-h, --help</tt></tag>
166 Print the short option summary shown above.
169 <tag><tt>-i, --ignore-case</tt></tag>
171 This option makes the assembler case insensitive on identifiers and labels.
172 This option will override the default, but may itself be overriden by the
173 <tt><ref id=".CASE" name=".CASE"></tt> control command.
176 <tag><tt>-l, --listing</tt></tag>
178 Generate an assembler listing. The listing file will always have the
179 name of the main input file with the extension replaced by ".lst". This
180 may change in future versions.
183 <tag><tt>--list-bytes n</tt></tag>
185 Set the maximum number of bytes printed in the listing for one line of
186 input. See the <tt><ref id=".LISTBYTES" name=".LISTBYTES"></tt> directive
187 for more information. The value zero can be used to encode an unlimited
188 number of printed bytes.
191 <tag><tt>-o name</tt></tag>
193 The default output name is the name of the input file with the extension
194 replaced by ".o". If you don't like that, you may give another name with
195 the -o option. The output file will be placed in the same directory as
196 the source file, or, if -o is given, the full path in this name is used.
199 <tag><tt>--pagelength n</tt></tag>
201 sets the length of a listing page in lines. See the <tt><ref
202 id=".PAGELENGTH" name=".PAGELENGTH"></tt> directive for more information.
205 <tag><tt>-s, --smart-mode</tt></tag>
207 In smart mode (enabled by -s or the <tt><ref id=".SMART" name=".SMART"></tt>
208 pseudo instruction) the assembler will track usage of the <tt/REP/ and
209 <tt/SEP/ instructions in 65816 mode and update the operand sizes
210 accordingly. If the operand of such an instruction cannot be evaluated by
211 the assembler (for example, because the operand is an imported symbol), a
214 Beware: Since the assembler cannot trace the execution flow this may
215 lead to false results in some cases. If in doubt, use the .ixx and .axx
216 instructions to tell the assembler about the current settings. Smart
217 mode is off by default.
220 <label id="option-t">
221 <tag><tt>-t sys, --target sys</tt></tag>
223 Set the target system. This will enable translation of character strings
224 and character constants into the character set of the target platform.
225 The default for the target system is "none", which means that no translation
226 will take place. The assembler supports the same target systems as the
227 compiler, see there for a list.
230 <tag><tt>-v, --verbose</tt></tag>
232 Increase the assembler verbosity. Usually only needed for debugging
233 purposes. You may use this option more than one time for even more
237 <tag><tt>-D</tt></tag>
239 This option allows you to define symbols on the command line. Without a
240 value, the symbol is defined with the value zero. When giving a value,
241 you may use the '$' prefix for hexadecimal symbols. Please note
242 that for some operating systems, '$' has a special meaning, so
243 you may have to quote the expression.
246 <tag><tt>-I dir, --include-dir dir</tt></tag>
248 Name a directory which is searched for include files. The option may be
249 used more than once to specify more than one directory to search. The
250 current directory is always searched first before considering any
251 additional directores.
254 <tag><tt>-U, --auto-import</tt></tag>
256 Mark symbols that are not defined in the sources as imported symbols. This
257 should be used with care since it delays error messages about typos and such
258 until the linker is run. The compiler uses the equivalent of this switch
259 (<tt><ref id=".AUTOIMPORT" name=".AUTOIMPORT"></tt>) to enable auto imported
260 symbols for the runtime library. However, the compiler is supposed to
261 generate code that runs through the assembler without problems, something
262 which is not always true for assembler programmers.
265 <tag><tt>-V, --version</tt></tag>
267 Print the version number of the assembler. If you send any suggestions
268 or bugfixes, please include the version number.
271 <label id="option-W">
272 <tag><tt>-Wn</tt></tag>
274 Set the warning level for the assembler. Using -W2 the assembler will
275 even warn about such things like unused imported symbols. The default
276 warning level is 1, and it would probably be silly to set it to
283 <sect>Input format<p>
285 <sect1>Assembler syntax<p>
287 The assembler accepts the standard 6502/65816 assembler syntax. One line may
288 contain a label (which is identified by a colon), and, in addition to the
289 label, an assembler mnemonic, a macro, or a control command (see section <ref
290 id="control-commands" name="Control Commands"> for supported control
291 commands). Alternatively, the line may contain a symbol definition using the
292 '=' token. Everything after a semicolon is handled as a comment (that is, it
295 Here are some examples for valid input lines:
298 Label: ; A label and a comment
299 lda #$20 ; A 6502 instruction plus comment
300 L1: ldx #$20 ; Same with label
301 L2: .byte "Hello world" ; Label plus control command
302 mymac $20 ; Macro expansion
303 MySym = 3*L1 ; Symbol definition
304 MaSym = Label ; Another symbol
307 The assembler accepts
310 <item>all valid 6502 mnemonics when in 6502 mode (the default or after the
311 <tt><ref id=".P02" name=".P02"></tt> command was given).
312 <item>all valid 6502 mnemonics plus a set of illegal instructions when in
313 <ref id="6502X-mode" name="6502X mode">.
314 <item>all valid 65SC02 mnemonics when in 65SC02 mode (after the
315 <tt><ref id=".PSC02" name=".PSC02"></tt> command was given).
316 <item>all valid 65C02 mnemonics when in 65C02 mode (after the
317 <tt><ref id=".PC02" name=".PC02"></tt> command was given).
318 <item>all valid 65618 mnemonics when in 65816 mode (after the
319 <tt><ref id=".P816" name=".P816"></tt> command was given).
320 <item>all valid SunPlus mnemonics when in SunPlus mode (after the
321 <tt><ref id=".SUNPLUS" name=".SUNPLUS"></tt> command was given).
327 In 65816 mode several aliases are accepted in addition to the official
331 BGE is an alias for BCS
332 BLT is an alias for BCC
333 CPA is an alias for CMP
334 DEA is an alias for DEC A
335 INA is an alias for INC A
336 SWA is an alias for XBA
337 TAD is an alias for TCD
338 TAS is an alias for TCS
339 TDA is an alias for TDC
340 TSA is an alias for TSC
345 <sect1>6502X mode<label id="6502X-mode"><p>
347 6502X mode is an extension to the normal 6502 mode. In this mode, several
348 mnemomics for illegal instructions of the NMOS 6502 CPUs are accepted. Since
349 these instructions are illegal, there are no official mnemonics for them. The
350 unofficial ones are taken from <htmlurl
351 url="http://oxyron.net/graham/opcodes02.html"
352 name="http://oxyron.net/graham/opcodes02.html">. Please note that only the
353 ones marked as "stable" are supported. The following table uses information
354 from the mentioned web page, for more information, see there.
357 <item><tt>ALR: A:=(A and #{imm})*2;</tt>
358 <item><tt>ANC: A:=A and #{imm};</tt> Generates opcode $0B.
359 <item><tt>ARR: A:=(A and #{imm})/2;</tt>
360 <item><tt>AXS: X:=A and X-#{imm};</tt>
361 <item><tt>DCP: {adr}:={adr}-1; A-{adr};</tt>
362 <item><tt>ISC: {adr}:={adr}+1; A:=A-{adr};</tt>
363 <item><tt>LAS: A,X,S:={adr} and S;</tt>
364 <item><tt>LAX: A,X:={adr};</tt>
365 <item><tt>RLA: {adr}:={adr}rol; A:=A and {adr};</tt>
366 <item><tt>RRA: {adr}:={adr}ror; A:=A adc {adr};</tt>
367 <item><tt>SAX: {adr}:=A and X;</tt>
368 <item><tt>SLO: {adr}:={adr}*2; A:=A or {adr};</tt>
369 <item><tt>SRE: {adr}:={adr}/2; A:=A xor {adr};</tt>
374 <sect1>sweet16 mode<label id="sweet16-mode"><p>
376 SWEET 16 is an interpreter for a pseudo 16 bit CPU written by Steve Wozniak
377 for the Apple ][ machines. It is available in the Apple ][ ROM. ca65 can
378 generate code for this pseudo CPU when switched into sweet16 mode. The
379 following is special in sweet16 mode:
383 <item>The '@' character denotes indirect addressing and is no longer available
384 for cheap local labels. If you need cheap local labels, you will have to
385 switch to another lead character using the <tt/<ref id=".LOCALCHAR"
386 name=".LOCALCHAR">/ command.
388 <item>Registers are specified using <tt/R0/ .. <tt/R15/. In sweet16 mode,
389 these identifiers are reserved words.
393 Please note that the assembler does neither supply the interpreter needed for
394 SWEET 16 code, nor the zero page locations needed for the SWEET 16 registers,
395 nor does it call the interpreter. All this must be done by your program. Apple
396 ][ programmers do probably know how to use sweet16 mode.
398 For more information about SWEET 16, see
399 <htmlurl url="http://www.6502.org/source/interpreters/sweet16.htm"
400 name="http://www.6502.org/source/interpreters/sweet16.htm">.
403 <sect1>Number format<p>
405 For literal values, the assembler accepts the widely used number formats:
406 A preceeding '$' denotes a hex value, a preceeding '%' denotes a
407 binary value, and a bare number is interpeted as a decimal. There are
408 currently no octal values and no floats.
411 <sect1>Conditional assembly<p>
413 Please note that when using the conditional directives (<tt/.IF/ and friends),
414 the input must consist of valid assembler tokens, even in <tt/.IF/ branches
415 that are not assembled. The reason for this behaviour is that the assembler
416 must still be able to detect the ending tokens (like <tt/.ENDIF/), so
417 conversion of the input stream into tokens still takes place. As a consequence
418 conditional assembly directives may <bf/not/ be used to prevent normal text
419 (used as a comment or similar) from being assembled. <p>
425 <sect1>Expression evaluation<p>
427 All expressions are evaluated with (at least) 32 bit precision. An
428 expression may contain constant values and any combination of internal and
429 external symbols. Expressions that cannot be evaluated at assembly time
430 are stored inside the object file for evaluation by the linker.
431 Expressions referencing imported symbols must always be evaluated by the
435 <sect1>Size of an expression result<p>
437 Sometimes, the assembler must know about the size of the value that is the
438 result of an expression. This is usually the case, if a decision has to be
439 made, to generate a zero page or an absolute memory references. In this
440 case, the assembler has to make some assumptions about the result of an
444 <item> If the result of an expression is constant, the actual value is
445 checked to see if it's a byte sized expression or not.
446 <item> If the expression is explicitly casted to a byte sized expression by
447 one of the '>', '<' or '^' operators, it is a byte expression.
448 <item> If this is not the case, and the expression contains a symbol,
449 explicitly declared as zero page symbol (by one of the .importzp or
450 .exportzp instructions), then the whole expression is assumed to be
452 <item> If the expression contains symbols that are not defined, and these
453 symbols are local symbols, the enclosing scopes are searched for a
454 symbol with the same name. If one exists and this symbol is defined,
455 it's attributes are used to determine the result size.
456 <item> In all other cases the expression is assumed to be word sized.
459 Note: If the assembler is not able to evaluate the expression at assembly
460 time, the linker will evaluate it and check for range errors as soon as
464 <sect1>Boolean expressions<p>
466 In the context of a boolean expression, any non zero value is evaluated as
467 true, any other value to false. The result of a boolean expression is 1 if
468 it's true, and zero if it's false. There are boolean operators with extrem
469 low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/
470 operators are shortcut operators. That is, if the result of the expression is
471 already known, after evaluating the left hand side, the right hand side is
475 <sect1>Constant expressions<p>
477 Sometimes an expression must evaluate to a constant without looking at any
478 further input. One such example is the <tt/<ref id=".IF" name=".IF">/ command
479 that decides if parts of the code are assembled or not. An expression used in
480 the <tt/.IF/ command cannot reference a symbol defined later, because the
481 decision about the <tt/.IF/ must be made at the point when it is read. If the
482 expression used in such a context contains only constant numerical values,
483 there is no problem. When unresolvable symbols are involved it may get harder
484 for the assembler to determine if the expression is actually constant, and it
485 is even possible to create expressions that aren't recognized as constant.
486 Simplifying the expressions will often help.
488 In cases where the result of the expression is not needed immediately, the
489 assembler will delay evaluation until all input is read, at which point all
490 symbols are known. So using arbitrary complex constant expressions is no
491 problem in most cases.
495 <sect1>Available operators<label id="operators"><p>
497 Available operators sorted by precedence:
500 Op Description Precedence
501 -------------------------------------------------------------------
502 Builtin string functions 0
504 Builtin pseudo variables 1
505 Builtin pseudo functions 1
508 ~ Unary bitwise not 1
509 .BITNOT Unary bitwise not 1
510 < Low byte operator 1
511 > High byte operator 1
512 ^ Bank byte operator 1
516 .MOD Modulo operation 2
518 .BITAND Bitwise and 2
520 .BITXOR Bitwise xor 2
521 << Shift left operator 2
522 .SHL Shift left operator 2
523 >> Shift right operator
524 .SHR Shift right operator 2
531 = Compare operation (equal) 4
532 <> Compare operation (not equal) 4
533 < Compare operation (less) 4
534 > Compare operation (greater) 4
535 <= Compare operation (less or equal) 4
536 >= Compare operation (greater or equal) 4
538 && Boolean and 5
550 To force a specific order of evaluation, braces may be used as usual.
556 <sect>Symbols and labels<p>
558 The assembler allows you to use symbols instead of naked values to make
559 the source more readable. There are a lot of different ways to define and
560 use symbols and labels, giving a lot of flexibility.
563 <sect1>Numeric constants<p>
565 Numeric constants are defined using the equal sign or the label assignment
566 operator. After doing
572 may use the symbol "two" in every place where a number is expected, and it is
573 evaluated to the value 2 in this context. The label assignment operator causes
574 the same, but causes the symbol to be marked as a label, which may cause a
575 different handling in the debugger:
581 The right side can of course be an expression:
588 <sect1>Standard labels<p>
590 A label is defined by writing the name of the label at the start of the line
591 (before any instruction mnemonic, macro or pseudo directive), followed by a
592 colon. This will declare a symbol with the given name and the value of the
593 current program counter.
596 <sect1>Local labels and symbols<p>
598 Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to
599 create regions of code where the names of labels and symbols are local to this
600 region. They are not known outside of this region and cannot be accessed from
601 there. Such regions may be nested like PROCEDUREs in Pascal.
603 See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
604 directive for more information.
607 <sect1>Cheap local labels<p>
609 Cheap local labels are defined like standard labels, but the name of the
610 label must begin with a special symbol (usually '@', but this can be
611 changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt>
614 Cheap local labels are visible only between two non cheap labels. As soon as a
615 standard symbol is encountered (this may also be a local symbol if inside a
616 region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the
617 cheap local symbol goes out of scope.
619 You may use cheap local labels as an easy way to reuse common label
620 names like "Loop". Here is an example:
623 Clear: lda #$00 ; Global label
625 @Loop: sta Mem,y ; Local label
629 Sub: ... ; New global label
630 bne @Loop ; ERROR: Unknown identifier!
633 <sect1>Unnamed labels<p>
635 If you really want to write messy code, there are also unnamed
636 labels. These labels do not have a name (you guessed that already,
637 didn't you?). A colon is used to mark the absence of the name.
639 Unnamed labels may be accessed by using the colon plus several minus
640 or plus characters as a label designator. Using the '-' characters
641 will create a back reference (use the n'th label backwards), using
642 '+' will create a forward reference (use the n'th label in forward
643 direction). An example will help to understand this:
665 As you can see from the example, unnamed labels will make even short
666 sections of code hard to understand, because you have to count labels
667 to find branch targets (this is the reason why I for my part do
668 prefer the "cheap" local labels). Nevertheless, unnamed labels are
669 convenient in some situations, so it's your decision.
672 <sect1>Using macros to define labels and constants<p>
674 While there are drawbacks with this approach, it may be handy in some
675 situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is
676 possible to define symbols or constants that may be used elsewhere. Since
677 the macro facility works on a very low level, there is no scoping. On the
678 other side, you may also define string constants this way (this is not
679 possible with the other symbol types).
685 .DEFINE version "SOS V2.3"
687 four = two * two ; Ok
690 .PROC ; Start local scope
691 two = 3 ; Will give "2 = 3" - invalid!
696 <sect1>Symbols and <tt>.DEBUGINFO</tt><p>
698 If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref
699 id="option-g" name="-g"> is given on the command line), global, local and
700 cheap local labels are written to the object file and will be available in the
701 symbol file via the linker. Unnamed labels are not written to the object file,
702 because they don't have a name which would allow to access them.
706 <sect>Scopes<label id="scopes"><p>
708 ca65 implements several sorts of scopes for symbols.
710 <sect1>Global scope<p>
712 All (non cheap local) symbols that are declared outside of any nested scopes
716 <sect1>A special scope: cheap locals<p>
718 A special scope is the scope for cheap local symbols. It lasts from one non
719 local symbol to the next one, without any provisions made by the programmer.
720 All other scopes differ in usage but use the same concept internally.
723 <sect1>Generic nested scopes<p>
725 A nested scoped for generic use is started with <tt/<ref id=".SCOPE"
726 name=".SCOPE">/ and closed with <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/.
727 The scope can have a name, in which case it is accessible from the outside by
728 using <ref id="scopesyntax" name="explicit scopes">. If the scope does not
729 have a name, all symbols created within the scope are local to the scope, and
730 aren't accessible from the outside.
732 A nested scope can access symbols from the local or from enclosing scopes by
733 name without using explicit scope names. In some cases there may be
734 ambiguities, for example if there is a reference to a local symbol that is not
735 yet defined, but a symbol with the same name exists in outer scopes:
747 In the example above, the <tt/lda/ instruction will load the value 3 into the
748 accumulator, because <tt/foo/ is redefined in the scope. However:
760 Here, <tt/lda/ will still load from <tt/$12,x/, but since it is unknown to the
761 assembler that <tt/foo/ is a zeropage symbol when translating the instruction,
762 absolute mode is used instead. In fact, the assembler will not use absolute
763 mode by default, but it will search through the enclosing scopes for a symbol
764 with the given name. If one is found, the address size of this symbol is used.
765 This may lead to errors:
777 In this case, when the assembler sees the symbol <tt/foo/ in the <tt/lda/
778 instruction, it will search for an already defined symbol <tt/foo/. It will
779 find <tt/foo/ in scope <tt/outer/, and a close look reveals that it is a
780 zeropage symbol. So the assembler will use zeropage addressing mode. If
781 <tt/foo/ is redefined later in scope <tt/inner/, the assembler tries to change
782 the address in the <tt/lda/ instruction already translated, but since the new
783 value needs absolute addressing mode, this fails, and an error message "Range
786 Of course the most simple solution for the problem is to move the definition
787 of <tt/foo/ in scope <tt/inner/ upwards, so it preceeds its use. There may be
788 rare cases when this cannot be done. In these cases, you can use one of the
789 address size override operators:
801 This will cause the <tt/lda/ instruction to be translated using absolute
802 addressing mode, which means changing the symbol reference later does not
806 <sect1>Nested procedures<p>
808 A nested procedure is created by use of <tt/<ref id=".PROC" name=".PROC">/. It
809 differs from a <tt/<ref id=".SCOPE" name=".SCOPE">/ in that it must have a
810 name, and a it will introduce a symbol with this name in the enclosing scope.
819 is actually the same as
828 This is the reason why a procedure must have a name. If you want a scope
829 without a name, use <tt/<ref id=".SCOPE" name=".SCOPE">/.
831 <bf/Note:/ As you can see from the example above, scopes and symbols live in
832 different namespaces. There can be a symbol named <tt/foo/ and a scope named
833 <tt/foo/ without any conflicts (but see the section titled <ref
834 id="scopesearch" name=""Scope search order"">).
837 <sect1>Structs, unions and enums<p>
839 Structs, unions and enums are explained in a <ref id="structs" name="separate
840 section">, I do only cover them here, because if they are declared with a
841 name, they open a nested scope, similar to <tt/<ref id=".SCOPE"
842 name=".SCOPE">/. However, when no name is specified, the behaviour is
843 different: In this case, no new scope will be opened, symbols declared within
844 a struct, union, or enum declaration will then be added to the enclosing scope
848 <sect1>Explicit scope specification<label id="scopesyntax"><p>
850 Accessing symbols from other scopes is possible by using an explicit scope
851 specification, provided that the scope where the symbol lives in has a name.
852 The namespace token (<tt/::/) is used to access other scopes:
860 lda foo::bar ; Access foo in scope bar
863 The only way to deny access to a scope from the outside is to declare a scope
864 without a name (using the <tt/<ref id=".SCOPE" name=".SCOPE">/ command).
866 A special syntax is used to specify the global scope: If a symbol or scope is
867 preceeded by the namespace token, the global scope is searched:
874 lda #::bar ; Access the global bar (which is 3)
879 <sect1>Scope search order<label id="scopesearch"><p>
881 The assembler searches for a scope in a similar way as for a symbol. First, it
882 looks in the current scope, and then it walks up the enclosing scopes until
885 However, one important thing to note when using explicit scope syntax is, that
886 a symbol may be accessed before it is defined, but a scope may <bf/not/ be
887 used without a preceeding definition. This means that in the following
896 lda #foo::bar ; Will load 3, not 2!
903 the reference to the scope <tt/foo/ will use the global scope, and not the
904 local one, because the local one is not visible at the point where it is
907 Things get more complex if a complete chain of scopes is specified:
918 lda #outer::inner::bar ; 1
930 When <tt/outer::inner::bar/ is referenced in the <tt/lda/ instruction, the
931 assembler will first search in the local scope for a scope named <tt/outer/.
932 Since none is found, the enclosing scope (<tt/another/) is checked. There is
933 still no scope named <tt/outer/, so scope <tt/foo/ is checked, and finally
934 scope <tt/outer/ is found. Within this scope, <tt/inner/ is searched, and in
935 this scope, the assembler looks for a symbol named <tt/bar/.
937 Please note that once the anchor scope is found, all following scopes
938 (<tt/inner/ in this case) are expected to be found exactly in this scope. The
939 assembler will search the scope tree only for the first scope (if it is not
940 anchored in the root scope). Starting from there on, there is no flexibility,
941 so if the scope named <tt/outer/ found by the assembler does not contain a
942 scope named <tt/inner/, this would be an error, even if such a pair does exist
943 (one level up in global scope).
945 Ambiguities that may be introduced by this search algorithm may be removed by
946 anchoring the scope specification in the global scope. In the example above,
947 if you want to access the "other" symbol <tt/bar/, you would have to write:
958 lda #::outer::inner::bar ; 2
971 <sect>Address sizes and memory models<label id="address-sizes"><p>
973 <sect1>Address sizes<p>
975 ca65 assigns each segment and each symbol an address size. This is true, even
976 if the symbol is not used as an address. You may also think of a value range
977 of the symbol instead of an address size.
979 Possible address sizes are:
982 <item>Zeropage or direct (8 bits)
983 <item>Absolute (16 bits)
988 Since the assembler uses default address sizes for the segments and symbols,
989 it is usually not necessary to override the default behaviour. In cases, where
990 it is necessary, the following keywords may be used to specify address sizes:
993 <item>DIRECT, ZEROPAGE or ZP for zeropage addressing (8 bits).
994 <item>ABSOLUTE, ABS or NEAR for absolute addressing (16 bits).
995 <item>FAR for far addressing (24 bits).
996 <item>LONG or DWORD for long addressing (32 bits).
1000 <sect1>Address sizes of segments<p>
1002 The assembler assigns an address size to each segment. Since the
1003 representation of a label within this segment is "segment start + offset",
1004 labels will inherit the address size of the segment they are declared in.
1006 The address size of a segment may be changed, by using an optional address
1007 size modifier. See the <tt/<ref id=".SEGMENT" name="segment directive">/ for
1008 an explanation on how this is done.
1011 <sect1>Address sizes of symbols<p>
1016 <sect1>Memory models<p>
1018 The default address size of a segment depends on the memory model used. Since
1019 labels inherit the address size from the segment they are declared in,
1020 changing the memory model is an easy way to change the address size of many
1026 <sect>Pseudo variables<label id="pseudo-variables"><p>
1028 Pseudo variables are readable in all cases, and in some special cases also
1031 <sect1><tt>*</tt><p>
1033 Reading this pseudo variable will return the program counter at the start
1034 of the current input line.
1036 Assignment to this variable is possible when <tt/<ref id=".FEATURE"
1037 name=".FEATURE pc_assignment">/ is used. Note: You should not use
1038 assignments to <tt/*/, use <tt/<ref id=".ORG" name=".ORG">/ instead.
1041 <sect1><tt>.CPU</tt><label id=".CPU"><p>
1043 Reading this pseudo variable will give a constant integer value that
1044 tells which CPU is currently enabled. It can also tell which instruction
1045 set the CPU is able to translate. The value read from the pseudo variable
1046 should be further examined by using one of the constants defined by the
1047 "cpu" macro package (see <tt/<ref id=".MACPACK" name=".MACPACK">/).
1049 It may be used to replace the .IFPxx pseudo instructions or to construct
1050 even more complex expressions.
1056 .if (.cpu .bitand CPU_ISET_65816)
1068 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
1070 This builtin pseudo variable is only available in macros. It is replaced by
1071 the actual number of parameters that were given in the macro invocation.
1076 .macro foo arg1, arg2, arg3
1077 .if .paramcount <> 3
1078 .error "Too few parameters for macro foo"
1084 See section <ref id="macros" name="Macros">.
1087 <sect1><tt>.TIME</tt><label id=".TIME"><p>
1089 Reading this pseudo variable will give a constant integer value that
1090 represents the current time in POSIX standard (as seconds since the
1093 It may be used to encode the time of translation somewhere in the created
1099 .dword .time ; Place time here
1103 <sect1><tt>.VERSION</tt><label id=".VERSION"><p>
1105 Reading this pseudo variable will give the assembler version according to
1106 the following formula:
1108 VER_MAJOR*$100 + VER_MINOR*$10 + VER_PATCH
1110 It may be used to encode the assembler version or check the assembler for
1111 special features not available with older versions.
1115 Version 2.11.1 of the assembler will return $2B1 as numerical constant when
1116 reading the pseudo variable <tt/.VERSION/.
1120 <sect>Pseudo functions<label id="pseudo-functions"><p>
1122 Pseudo functions expect their arguments in parenthesis, and they have a result,
1123 either a string or an expression.
1126 <sect1><tt>.BANKBYTE</tt><label id=".BANKBYTE"><p>
1128 The function returns the bank byte (that is, bits 16-23) of its argument.
1129 It works identical to the '^' operator.
1131 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1132 <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>
1135 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
1137 Builtin function. The function evaluates its argument in braces and yields
1138 "false" if the argument is non blank (there is an argument), and "true" if
1139 there is no argument. The token list that makes up the function argument
1140 may optionally be enclosed in curly braces. This allows the inclusion of
1141 tokens that would otherwise terminate the list (the closing right
1142 parenthesis). The curly braces are not considered part of the list, a list
1143 just consisting of curly braces is considered to be empty.
1145 As an example, the <tt/.IFBLANK/ statement may be replaced by
1153 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
1155 Builtin string function. The function allows to concatenate a list of string
1156 constants separated by commas. The result is a string constant that is the
1157 concatentation of all arguments. This function is most useful in macros and
1158 when used together with the <tt/.STRING/ builtin function. The function may
1159 be used in any case where a string constant is expected.
1164 .include .concat ("myheader", ".", "inc")
1167 This is the same as the command
1170 .include "myheader.inc"
1174 <sect1><tt>.CONST</tt><label id=".CONST"><p>
1176 Builtin function. The function evaluates its argument in braces and
1177 yields "true" if the argument is a constant expression (that is, an
1178 expression that yields a constant value at assembly time) and "false"
1179 otherwise. As an example, the .IFCONST statement may be replaced by
1186 <sect1><tt>.HIBYTE</tt><label id=".HIBYTE"><p>
1188 The function returns the high byte (that is, bits 8-15) of its argument.
1189 It works identical to the '>' operator.
1191 See: <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>,
1192 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1195 <sect1><tt>.HIWORD</tt><label id=".HIWORD"><p>
1197 The function returns the high word (that is, bits 16-31) of its argument.
1199 See: <tt><ref id=".LOWORD" name=".LOWORD"></tt>
1202 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1204 Builtin function. Extracts the left part of a given token list.
1209 .LEFT (<int expr>, <token list>)
1212 The first integer expression gives the number of tokens to extract from
1213 the token list. The second argument is the token list itself. The token
1214 list may optionally be enclosed into curly braces. This allows the
1215 inclusion of tokens that would otherwise terminate the list (the closing
1216 right paren in the given case).
1220 To check in a macro if the given argument has a '#' as first token
1221 (immidiate addressing mode), use something like this:
1226 .if (.match (.left (1, {arg}), #))
1228 ; ldax called with immidiate operand
1236 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1237 name=".RIGHT"></tt> builtin functions.
1240 <sect1><tt>.LOBYTE</tt><label id=".LOBYTE"><p>
1242 The function returns the low byte (that is, bits 0-7) of its argument.
1243 It works identical to the '<' operator.
1245 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1246 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1249 <sect1><tt>.LOWORD</tt><label id=".LOWORD"><p>
1251 The function returns the low word (that is, bits 0-15) of its argument.
1253 See: <tt><ref id=".HIWORD" name=".HIWORD"></tt>
1256 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1258 Builtin function. Matches two token lists against each other. This is
1259 most useful within macros, since macros are not stored as strings, but
1265 .MATCH(<token list #1>, <token list #2>)
1268 Both token list may contain arbitrary tokens with the exception of the
1269 terminator token (comma resp. right parenthesis) and
1276 The token lists may optionally be enclosed into curly braces. This allows
1277 the inclusion of tokens that would otherwise terminate the list (the closing
1278 right paren in the given case). Often a macro parameter is used for any of
1281 Please note that the function does only compare tokens, not token
1282 attributes. So any number is equal to any other number, regardless of the
1283 actual value. The same is true for strings. If you need to compare tokens
1284 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1285 name=".XMATCH"></tt> function.
1289 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1290 while honoring the sign bit. The builtin processor instructions will allow
1291 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1292 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1293 to check for this and print and error for invalid calls.
1298 .if (.not .blank(arg)) .and (.not .match ({arg}, a))
1299 .error "Syntax error"
1302 cmp #$80 ; Bit 7 into carry
1303 lsr a ; Shift carry into bit 7
1308 The macro will only accept no arguments, or one argument that must be the
1309 reserved keyword "A".
1311 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1314 <sect1><tt>.MID</tt><label id=".MID"><p>
1316 Builtin function. Takes a starting index, a count and a token list as
1317 arguments. Will return part of the token list.
1322 .MID (<int expr>, <int expr>, <token list>)
1325 The first integer expression gives the starting token in the list (the first
1326 token has index 0). The second integer expression gives the number of tokens
1327 to extract from the token list. The third argument is the token list itself.
1328 The token list may optionally be enclosed into curly braces. This allows the
1329 inclusion of tokens that would otherwise terminate the list (the closing
1330 right paren in the given case).
1334 To check in a macro if the given argument has a '<tt/#/' as first token
1335 (immidiate addressing mode), use something like this:
1340 .if (.match (.mid (0, 1, {arg}), #))
1342 ; ldax called with immidiate operand
1350 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1351 name=".RIGHT"></tt> builtin functions.
1354 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
1356 Builtin function. The function expects an identifier as argument in braces.
1357 The argument is evaluated, and the function yields "true" if the identifier
1358 is a symbol that has already been referenced somewhere in the source file up
1359 to the current position. Otherwise the function yields false. As an example,
1360 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
1366 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1369 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
1371 Builtin function. Extracts the right part of a given token list.
1376 .RIGHT (<int expr>, <token list>)
1379 The first integer expression gives the number of tokens to extract from the
1380 token list. The second argument is the token list itself. The token list
1381 may optionally be enclosed into curly braces. This allows the inclusion of
1382 tokens that would otherwise terminate the list (the closing right paren in
1385 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
1386 name=".MID"></tt> builtin functions.
1389 <sect1><tt>.SIZEOF</tt><label id=".SIZEOF"><p>
1391 <tt/.SIZEOF/ is a pseudo function that returns the size of its argument. The
1392 argument can be a struct/union, a struct member, a procedure, or a label. In
1393 case of a procedure or label, its size is defined by the amount of data
1394 placed in the segment where the label is relative to. If a line of code
1395 switches segments (for example in a macro) data placed in other segments
1396 does not count for the size.
1398 Please note that a symbol or scope must exist, before it is used together with
1399 <tt/.SIZEOF/ (this may get relaxed later, but will always be true for scopes).
1400 A scope has preference over a symbol with the same name, so if the last part
1401 of a name represents both, a scope and a symbol, the scope is choosen over the
1404 After the following code:
1407 .struct Point ; Struct size = 4
1412 P: .tag Point ; Declare a point
1413 @P: .tag Point ; Declare another point
1425 .data ; Segment switch!!!
1431 <tag><tt/.sizeof(Point)/</tag>
1432 will have the value 4, because this is the size of struct <tt/Point/.
1434 <tag><tt/.sizeof(Point::xcoord)/</tag>
1435 will have the value 2, because this is the size of the member <tt/xcoord/
1436 in struct <tt/Point/.
1438 <tag><tt/.sizeof(P)/</tag>
1439 will have the value 4, this is the size of the data declared on the same
1440 source line as the label <tt/P/, which is in the same segment that <tt/P/
1443 <tag><tt/.sizeof(@P)/</tag>
1444 will have the value 4, see above. The example demonstrates that <tt/.SIZEOF/
1445 does also work for cheap local symbols.
1447 <tag><tt/.sizeof(Code)/</tag>
1448 will have the value 3, since this is amount of data emitted into the code
1449 segment, the segment that was active when <tt/Code/ was entered. Note that
1450 this value includes the amount of data emitted in child scopes (in this
1451 case <tt/Code::Inner/).
1453 <tag><tt/.sizeof(Code::Inner)/</tag>
1454 will have the value 1 as expected.
1456 <tag><tt/.sizeof(Data)/</tag>
1457 will have the value 0. Data is emitted within the scope <tt/Data/, but since
1458 the segment is switched after entry, this data is emitted into another
1463 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
1465 Builtin function. The function accepts a string and an index as
1466 arguments and returns the value of the character at the given position
1467 as an integer value. The index is zero based.
1473 ; Check if the argument string starts with '#'
1474 .if (.strat (Arg, 0) = '#')
1481 <sect1><tt>.STRING</tt><label id=".STRING"><p>
1483 Builtin function. The function accepts an argument in braces and converts
1484 this argument into a string constant. The argument may be an identifier, or
1485 a constant numeric value.
1487 Since you can use a string in the first place, the use of the function may
1488 not be obvious. However, it is useful in macros, or more complex setups.
1493 ; Emulate other assemblers:
1495 .segment .string(name)
1500 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
1502 Builtin function. The function accepts a string argument in braces and
1503 eveluates to the length of the string.
1507 The following macro encodes a string as a pascal style string with
1508 a leading length byte.
1512 .byte .strlen(Arg), Arg
1517 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
1519 Builtin function. The function accepts a token list in braces. The function
1520 result is the number of tokens given as argument. The token list may
1521 optionally be enclosed into curly braces which are not considered part of
1522 the list and not counted. Enclosement in curly braces allows the inclusion
1523 of tokens that would otherwise terminate the list (the closing right paren
1528 The <tt/ldax/ macro accepts the '#' token to denote immidiate addressing (as
1529 with the normal 6502 instructions). To translate it into two separate 8 bit
1530 load instructions, the '#' token has to get stripped from the argument:
1534 .if (.match (.mid (0, 1, {arg}), #))
1535 ; ldax called with immidiate operand
1536 lda #<(.right (.tcount ({arg})-1, {arg}))
1537 ldx #>(.right (.tcount ({arg})-1, {arg}))
1545 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
1547 Builtin function. Matches two token lists against each other. This is
1548 most useful within macros, since macros are not stored as strings, but
1554 .XMATCH(<token list #1>, <token list #2>)
1557 Both token list may contain arbitrary tokens with the exception of the
1558 terminator token (comma resp. right parenthesis) and
1565 The token lists may optionally be enclosed into curly braces. This allows
1566 the inclusion of tokens that would otherwise terminate the list (the closing
1567 right paren in the given case). Often a macro parameter is used for any of
1570 The function compares tokens <em/and/ token values. If you need a function
1571 that just compares the type of tokens, have a look at the <tt><ref
1572 id=".MATCH" name=".MATCH"></tt> function.
1574 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
1578 <sect>Control commands<label id="control-commands"><p>
1580 Here's a list of all control commands and a description, what they do:
1583 <sect1><tt>.A16</tt><label id=".A16"><p>
1585 Valid only in 65816 mode. Switch the accumulator to 16 bit.
1587 Note: This command will not emit any code, it will tell the assembler to
1588 create 16 bit operands for immediate accumulator adressing mode.
1590 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1593 <sect1><tt>.A8</tt><label id=".A8"><p>
1595 Valid only in 65816 mode. Switch the accumulator to 8 bit.
1597 Note: This command will not emit any code, it will tell the assembler to
1598 create 8 bit operands for immediate accu adressing mode.
1600 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1603 <sect1><tt>.ADDR</tt><label id=".ADDR"><p>
1605 Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and
1606 may be used for better readability if the data words are address values. In
1607 65816 mode, the address is forced to be 16 bit wide to fit into the current
1608 segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command
1609 must be followed by a sequence of (not necessarily constant) expressions.
1614 .addr $0D00, $AF13, _Clear
1617 See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD"
1621 <sect1><tt>.ALIGN</tt><label id=".ALIGN"><p>
1623 Align data to a given boundary. The command expects a constant integer
1624 argument that must be a power of two, plus an optional second argument
1625 in byte range. If there is a second argument, it is used as fill value,
1626 otherwise the value defined in the linker configuration file is used
1627 (the default for this value is zero).
1629 Since alignment depends on the base address of the module, you must
1630 give the same (or a greater) alignment for the segment when linking.
1631 The linker will give you a warning, if you don't do that.
1640 <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"><p>
1642 Define a string with a trailing zero.
1647 Msg: .asciiz "Hello world"
1650 This will put the string "Hello world" followed by a binary zero into
1651 the current segment. There may be more strings separated by commas, but
1652 the binary zero is only appended once (after the last one).
1655 <sect1><tt>.ASSERT</tt><label id=".ASSERT"><p>
1657 Add an assertion. The command is followed by an expression, an action
1658 specifier and a message that is output in case the assertion fails. The
1659 action specifier may be one of <tt/warning/ or <tt/error/. The assertion
1660 is passed to the linker and will be evaluated when segment placement has
1666 .assert * = $8000, error, "Code not at $8000"
1669 The example assertion will check that the current location is at $8000,
1670 when the output file is written, and abort with an error if this is not
1671 the case. More complex expressions are possible. The action specifier
1672 <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs
1673 an error message. In the latter case, generation if the output file is
1677 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
1679 Is followed by a plus or a minus character. When switched on (using a
1680 +), undefined symbols are automatically marked as import instead of
1681 giving errors. When switched off (which is the default so this does not
1682 make much sense), this does not happen and an error message is
1683 displayed. The state of the autoimport flag is evaluated when the
1684 complete source was translated, before outputing actual code, so it is
1685 <em/not/ possible to switch this feature on or off for separate sections
1686 of code. The last setting is used for all symbols.
1688 You should probably not use this switch because it delays error
1689 messages about undefined symbols until the link stage. The cc65
1690 compiler (which is supposed to produce correct assembler code in all
1691 circumstances, something which is not true for most assembler
1692 programmers) will insert this command to avoid importing each and every
1693 routine from the runtime library.
1698 .autoimport + ; Switch on auto import
1702 <sect1><tt>.BSS</tt><label id=".BSS"><p>
1704 Switch to the BSS segment. The name of the BSS segment is always "BSS",
1705 so this is a shortcut for
1711 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1714 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
1716 Define byte sized data. Must be followed by a sequence of (byte ranged)
1717 expressions or strings.
1723 .byt "world", $0D, $00
1727 <sect1><tt>.CASE</tt><label id=".CASE"><p>
1729 Switch on or off case sensitivity on identifiers. The default is off
1730 (that is, identifiers are case sensitive), but may be changed by the
1731 -i switch on the command line.
1732 The command must be followed by a '+' or '-' character to switch the
1733 option on or off respectively.
1738 .case - ; Identifiers are not case sensitive
1742 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
1744 Apply a custom mapping for characters. The command is followed by two
1745 numbers in the range 1..255. The first one is the index of the source
1746 character, the second one is the mapping. The mapping applies to all
1747 character and string constants when they generate output, and overrides
1748 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
1749 command line switch.
1754 .charmap $41, $61 ; Map 'A' to 'a'
1758 <sect1><tt>.CODE</tt><label id=".CODE"><p>
1760 Switch to the CODE segment. The name of the CODE segment is always
1761 "CODE", so this is a shortcut for
1767 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1770 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
1772 Export a symbol and mark it in a special way. The linker is able to build
1773 tables of all such symbols. This may be used to automatically create a list
1774 of functions needed to initialize linked library modules.
1776 Note: The linker has a feature to build a table of marked routines, but it
1777 is your code that must call these routines, so just declaring a symbol with
1778 <tt/.CONDES/ does nothing by itself.
1780 All symbols are exported as an absolute (16 bit) symbol. You don't need to
1781 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
1782 is implied by <tt/.CONDES/.
1784 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
1785 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
1786 specifiying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
1787 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
1788 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
1789 name=".INTERRUPTORCONSTRUCTOR"></tt>commands are actually shortcuts
1790 for <tt/.CONDES/ with a type of <tt/constructor/ resp. <tt/destructor/ or
1793 After the type, an optional priority may be specified. Higher numeric values
1794 mean higher priority. If no priority is given, the default priority of 7 is
1795 used. Be careful when assigning priorities to your own module constructors
1796 so they won't interfere with the ones in the cc65 library.
1801 .condes ModuleInit, constructor
1802 .condes ModInit, 0, 16
1805 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
1806 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
1807 name=".INTERRUPTOR"></tt>commands and the separate section <ref id="condes"
1808 name="Module constructors/destructors"> explaining the feature in more
1812 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
1814 Export a symbol and mark it as a module constructor. This may be used
1815 together with the linker to build a table of constructor subroutines that
1816 are called by the startup code.
1818 Note: The linker has a feature to build a table of marked routines, but it
1819 is your code that must call these routines, so just declaring a symbol as
1820 constructor does nothing by itself.
1822 A constructor is always exported as an absolute (16 bit) symbol. You don't
1823 need to use an additional <tt/.export/ statement, this is implied by
1824 <tt/.constructor/. It may have an optional priority that is separated by a
1825 comma. Higher numeric values mean a higher priority. If no priority is
1826 given, the default priority of 7 is used. Be careful when assigning
1827 priorities to your own module constructors so they won't interfere with the
1828 ones in the cc65 library.
1833 .constructor ModuleInit
1834 .constructor ModInit, 16
1837 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1838 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
1839 <ref id="condes" name="Module constructors/destructors"> explaining the
1840 feature in more detail.
1843 <sect1><tt>.DATA</tt><label id=".DATA"><p>
1845 Switch to the DATA segment. The name of the DATA segment is always
1846 "DATA", so this is a shortcut for
1852 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1855 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
1857 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
1858 create word sized data in native 65XX format). Must be followed by a
1859 sequence of (word ranged) expressions.
1867 This will emit the bytes
1873 into the current segment in that order.
1876 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
1878 Switch on or off debug info generation. The default is off (that is,
1879 the object file will not contain debug infos), but may be changed by the
1880 -g switch on the command line.
1881 The command must be followed by a '+' or '-' character to switch the
1882 option on or off respectively.
1887 .debuginfo + ; Generate debug info
1891 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
1893 Start a define style macro definition. The command is followed by an
1894 identifier (the macro name) and optionally by a list of formal arguments
1896 See section <ref id="macros" name="Macros">.
1899 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
1901 Builtin function. The function expects an identifier as argument in braces.
1902 The argument is evaluated, and the function yields "true" if the identifier
1903 is a symbol that is already defined somewhere in the source file up to the
1904 current position. Otherwise the function yields false. As an example, the
1905 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
1912 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
1914 Export a symbol and mark it as a module destructor. This may be used
1915 together with the linker to build a table of destructor subroutines that
1916 are called by the startup code.
1918 Note: The linker has a feature to build a table of marked routines, but it
1919 is your code that must call these routines, so just declaring a symbol as
1920 constructor does nothing by itself.
1922 A destructor is always exported as an absolute (16 bit) symbol. You don't
1923 need to use an additional <tt/.export/ statement, this is implied by
1924 <tt/.destructor/. It may have an optional priority that is separated by a
1925 comma. Higher numerical values mean a higher priority. If no priority is
1926 given, the default priority of 7 is used. Be careful when assigning
1927 priorities to your own module destructors so they won't interfere with the
1928 ones in the cc65 library.
1933 .destructor ModuleDone
1934 .destructor ModDone, 16
1937 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1938 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
1939 section <ref id="condes" name="Module constructors/destructors"> explaining
1940 the feature in more detail.
1943 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
1945 Define dword sized data (4 bytes) Must be followed by a sequence of
1951 .dword $12344512, $12FA489
1955 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
1957 Conditional assembly: Reverse the current condition.
1960 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
1962 Conditional assembly: Reverse current condition and test a new one.
1965 <sect1><tt>.END</tt><label id=".END"><p>
1967 Forced end of assembly. Assembly stops at this point, even if the command
1968 is read from an include file.
1971 <sect1><tt>.ENDENUM</tt><label id=".ENDENUM"><p>
1973 End a <tt><ref id=".ENUM" name=".ENUM"></tt> declaration.
1976 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
1978 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
1979 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
1982 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
1984 End of macro definition (see section <ref id="macros" name="Macros">).
1987 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
1989 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
1992 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
1994 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
1997 <sect1><tt>.ENDSCOPE</tt><label id=".ENDSCOPE"><p>
1999 End of local lexical level (see <tt/<ref id=".SCOPE" name=".SCOPE">/).
2002 <sect1><tt>.ENDSTRUCT</tt><label id=".ENDSTRUCT"><p>
2004 Ends a struct definition. See the <tt/<ref id=".STRUCT" name=".STRUCT">/
2005 command and the separate section named <ref id="structs" name=""Structs
2009 <sect1><tt>.ENUM</tt><label id=".ENUM"><p>
2011 Start an enumeration. This directive is very similar to the C <tt/enum/
2012 keyword. If a name is given, a new scope is created for the enumeration,
2013 otherwise the enumeration members are placed in the enclosing scope.
2015 In the enumeration body, symbols are declared. The first symbol has a value
2016 of zero, and each following symbol will get the value of the preceeding plus
2017 one. This behaviour may be overriden by an explicit assignment. Two symbols
2018 may have the same value.
2030 Above example will create a new scope named <tt/errorcodes/ with three
2031 symbols in it that get the values 0, 1 and 2 respectively. Another way
2032 to write this would have been:
2042 Please note that explicit scoping must be used to access the identifiers:
2045 .word errorcodes::no_error
2048 A more complex example:
2057 EWOULDBLOCK = EAGAIN
2061 In this example, the enumeration does not have a name, which means that the
2062 members will be visible in the enclosing scope and can be used in this scope
2063 without explicit scoping. The first member (<tt/EUNKNOWN/) has the value -1.
2064 The value for the following members is incremented by one, so <tt/EOK/ would
2065 be zero and so on. <tt/EWOULDBLOCK/ is an alias for <tt/EGAIN/, so it has an
2066 override for the value using an already defined symbol.
2069 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
2071 Force an assembly error. The assembler will output an error message
2072 preceeded by "User error" and will <em/not/ produce an object file.
2074 This command may be used to check for initial conditions that must be
2075 set before assembling a source file.
2085 .error "Must define foo or bar!"
2089 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
2090 id=".OUT" name=".OUT"></tt> directives.
2093 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
2095 Abort a macro expansion immidiately. This command is often useful in
2096 recursive macros. See separate section <ref id="macros" name="Macros">.
2099 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
2101 Make symbols accessible from other modules. Must be followed by a comma
2102 separated list of symbols to export, with each one optionally followed by
2103 an address specification. The default is to export the symbol with the
2104 address size it actually has. The assembler will issue a warning, if the
2105 symbol is exported with an address size smaller than the actual address
2115 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
2118 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
2120 Make symbols accessible from other modules. Must be followed by a comma
2121 separated list of symbols to export. The exported symbols are explicitly
2122 marked as zero page symols.
2130 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
2133 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
2135 Define far (24 bit) address data. The command must be followed by a
2136 sequence of (not necessarily constant) expressions.
2141 .faraddr DrawCircle, DrawRectangle, DrawHexagon
2144 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
2147 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
2149 This directive may be used to enable one or more compatibility features
2150 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
2151 possible, it may be useful when porting sources written for other
2152 assemblers. There is no way to switch a feature off, once you have
2153 enabled it, so using
2159 will enable the feature until end of assembly is reached.
2161 The following features are available:
2165 <tag><tt>at_in_identifiers</tt></tag>
2167 Accept the at character (`@') as a valid character in identifiers. The
2168 at character is not allowed to start an identifier, even with this
2171 <tag><tt>dollar_in_identifiers</tt></tag>
2173 Accept the dollar sign (`$') as a valid character in identifiers. The
2174 at character is not allowed to start an identifier, even with this
2177 <tag><tt>dollar_is_pc</tt></tag>
2179 The dollar sign may be used as an alias for the star (`*'), which
2180 gives the value of the current PC in expressions.
2181 Note: Assignment to the pseudo variable is not allowed.
2183 <tag><tt>labels_without_colons</tt></tag>
2185 Allow labels without a trailing colon. These labels are only accepted,
2186 if they start at the beginning of a line (no leading white space).
2188 <tag><tt>leading_dot_in_identifiers</tt></tag>
2190 Accept the dot (`.') as the first character of an identifier. This may be
2191 used for example to create macro names that start with a dot emulating
2192 control directives of other assemblers. Note however, that none of the
2193 reserved keywords built into the assembler, that starts with a dot, may be
2194 overridden. When using this feature, you may also get into trouble if
2195 later versions of the assembler define new keywords starting with a dot.
2197 <tag><tt>loose_char_term</tt></tag>
2199 Accept single quotes as well as double quotes as terminators for char
2202 <tag><tt>loose_string_term</tt></tag>
2204 Accept single quotes as well as double quotes as terminators for string
2207 <tag><tt>missing_char_term</tt></tag>
2209 Accept single quoted character constants where the terminating quote is
2214 <bf/Note:/ This does not work in conjunction with <tt/.FEATURE
2215 loose_string_term/, since in this case the input would be ambigous.
2217 <tag><tt>pc_assignment</tt></tag>
2219 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
2220 is enabled). Such an assignment is handled identical to the <tt><ref
2221 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
2222 removing the lines with the assignments may also be an option when porting
2223 code written for older assemblers).
2225 <tag><tt>ubiquitous_idents</tt></tag>
2227 Allow the use of instructions names as names for macros and symbols. This
2228 makes it possible to "overload" instructions by defining a macro with the
2229 same name. This does also make it possible to introduce hard to find errors
2230 in your code, so be careful!
2234 It is also possible to specify features on the command line using the
2235 <tt><ref id="option--feature" name="--feature"></tt> command line option.
2236 This is useful when translating sources written for older assemblers, when
2237 you don't want to change the source code.
2239 As an example, to translate sources written for Andre Fachats xa65
2240 assembler, the features
2243 labels_without_colons, pc_assignment, loose_char_term
2246 may be helpful. They do not make ca65 completely compatible, so you may not
2247 be able to translate the sources without changes, even when enabling these
2248 features. However, I have found several sources that translate without
2249 problems when enabling these features on the command line.
2252 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
2254 Insert an option string into the object file. There are two forms of
2255 this command, one specifies the option by a keyword, the second
2256 specifies it as a number. Since usage of the second one needs knowledge
2257 of the internal encoding, its use is not recommended and I will only
2258 describe the first form here.
2260 The command is followed by one of the keywords
2268 a comma and a string. The option is written into the object file
2269 together with the string value. This is currently unidirectional and
2270 there is no way to actually use these options once they are in the
2276 .fileopt comment, "Code stolen from my brother"
2277 .fileopt compiler, "BASIC 2.0"
2278 .fopt author, "J. R. User"
2282 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
2284 Import an absolute symbol from another module. The command is followed by a
2285 comma separated list of symbols to import. The command is similar to <tt>
2286 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
2287 written to the generated object file, even if the symbol is never referenced
2288 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
2289 references for unused symbols).
2294 .forceimport needthisone, needthistoo
2297 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2300 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
2302 Declare symbols as global. Must be followed by a comma separated list of
2303 symbols to declare. Symbols from the list, that are defined somewhere in the
2304 source, are exported, all others are imported. Additional <tt><ref
2305 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
2306 name=".EXPORT"></tt> commands for the same symbol are allowed.
2315 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
2317 Declare symbols as global. Must be followed by a comma separated list of
2318 symbols to declare. Symbols from the list, that are defined somewhere in the
2319 source, are exported, all others are imported. Additional <tt><ref
2320 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
2321 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
2322 in the list are explicitly marked as zero page symols.
2331 <sect1><tt>.I16</tt><label id=".I16"><p>
2333 Valid only in 65816 mode. Switch the index registers to 16 bit.
2335 Note: This command will not emit any code, it will tell the assembler to
2336 create 16 bit operands for immediate operands.
2338 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
2339 name=".SMART"></tt> commands.
2342 <sect1><tt>.I8</tt><label id=".I8"><p>
2344 Valid only in 65816 mode. Switch the index registers to 8 bit.
2346 Note: This command will not emit any code, it will tell the assembler to
2347 create 8 bit operands for immediate operands.
2349 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
2350 name=".SMART"></tt> commands.
2353 <sect1><tt>.IF</tt><label id=".IF"><p>
2355 Conditional assembly: Evalute an expression and switch assembler output
2356 on or off depending on the expression. The expression must be a constant
2357 expression, that is, all operands must be defined.
2359 A expression value of zero evaluates to FALSE, any other value evaluates
2363 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
2365 Conditional assembly: Check if there are any remaining tokens in this line,
2366 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
2367 condition is not true, further lines are not assembled until an <tt><ref
2368 id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2369 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2371 This command is often used to check if a macro parameter was given. Since an
2372 empty macro parameter will evaluate to nothing, the condition will evaluate
2373 to FALSE if an empty parameter was given.
2387 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2390 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
2392 Conditional assembly: Evaluate an expression and switch assembler output
2393 on or off depending on the constness of the expression.
2395 A const expression evaluates to to TRUE, a non const expression (one
2396 containing an imported or currently undefined symbol) evaluates to
2399 See also: <tt><ref id=".CONST" name=".CONST"></tt>
2402 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
2404 Conditional assembly: Check if a symbol is defined. Must be followed by
2405 a symbol name. The condition is true if the the given symbol is already
2406 defined, and false otherwise.
2408 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2411 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
2413 Conditional assembly: Check if there are any remaining tokens in this line,
2414 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
2415 condition is not true, further lines are not assembled until an <tt><ref
2416 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2417 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2419 This command is often used to check if a macro parameter was given.
2420 Since an empty macro parameter will evaluate to nothing, the condition
2421 will evaluate to FALSE if an empty parameter was given.
2434 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2437 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
2439 Conditional assembly: Check if a symbol is defined. Must be followed by
2440 a symbol name. The condition is true if the the given symbol is not
2441 defined, and false otherwise.
2443 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2446 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
2448 Conditional assembly: Check if a symbol is referenced. Must be followed
2449 by a symbol name. The condition is true if if the the given symbol was
2450 not referenced before, and false otherwise.
2452 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2455 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
2457 Conditional assembly: Check if the assembler is currently in 6502 mode
2458 (see <tt><ref id=".P02" name=".P02"></tt> command).
2461 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
2463 Conditional assembly: Check if the assembler is currently in 65816 mode
2464 (see <tt><ref id=".P816" name=".P816"></tt> command).
2467 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
2469 Conditional assembly: Check if the assembler is currently in 65C02 mode
2470 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
2473 <sect1><tt>.IFPSC02</tt><label id=".IFPSC02"><p>
2475 Conditional assembly: Check if the assembler is currently in 65SC02 mode
2476 (see <tt><ref id=".PSC02" name=".PSC02"></tt> command).
2479 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
2481 Conditional assembly: Check if a symbol is referenced. Must be followed
2482 by a symbol name. The condition is true if if the the given symbol was
2483 referenced before, and false otherwise.
2485 This command may be used to build subroutine libraries in include files
2486 (you may use separate object modules for this purpose too).
2491 .ifref ToHex ; If someone used this subroutine
2492 ToHex: tay ; Define subroutine
2498 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2501 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
2503 Import a symbol from another module. The command is followed by a comma
2504 separated list of symbols to import, with each one optionally followed by
2505 an address specification.
2511 .import bar: zeropage
2514 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
2517 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
2519 Import a symbol from another module. The command is followed by a comma
2520 separated list of symbols to import. The symbols are explicitly imported
2521 as zero page symbols (that is, symbols with values in byte range).
2529 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2532 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
2534 Include a file as binary data. The command expects a string argument
2535 that is the name of a file to include literally in the current segment.
2536 In addition to that, a start offset and a size value may be specified,
2537 separated by commas. If no size is specified, all of the file from the
2538 start offset to end-of-file is used. If no start position is specified
2539 either, zero is assumed (which means that the whole file is inserted).
2544 ; Include whole file
2545 .incbin "sprites.dat"
2547 ; Include file starting at offset 256
2548 .incbin "music.dat", $100
2550 ; Read 100 bytes starting at offset 200
2551 .incbin "graphics.dat", 200, 100
2555 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
2557 Include another file. Include files may be nested up to a depth of 16.
2566 <sect1><tt>.INTERRUPTOR</tt><label id=".INTERRUPTOR"><p>
2568 Export a symbol and mark it as an interruptor. This may be used together
2569 with the linker to build a table of interruptor subroutines that are called
2572 Note: The linker has a feature to build a table of marked routines, but it
2573 is your code that must call these routines, so just declaring a symbol as
2574 interruptor does nothing by itself.
2576 An interruptor is always exported as an absolute (16 bit) symbol. You don't
2577 need to use an additional <tt/.export/ statement, this is implied by
2578 <tt/.interruptor/. It may have an optional priority that is separated by a
2579 comma. Higher numeric values mean a higher priority. If no priority is
2580 given, the default priority of 7 is used. Be careful when assigning
2581 priorities to your own module constructors so they won't interfere with the
2582 ones in the cc65 library.
2587 .interruptor IrqHandler
2588 .interruptor Handler, 16
2591 See the <tt><ref id=".CONDES" name=".CONDES"></tt> command and the separate
2592 section <ref id="condes" name="Module constructors/destructors"> explaining
2593 the feature in more detail.
2596 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
2598 Switch on or off line continuations using the backslash character
2599 before a newline. The option is off by default.
2600 Note: Line continuations do not work in a comment. A backslash at the
2601 end of a comment is treated as part of the comment and does not trigger
2603 The command must be followed by a '+' or '-' character to switch the
2604 option on or off respectively.
2609 .linecont + ; Allow line continuations
2612 #$20 ; This is legal now
2616 <sect1><tt>.LIST</tt><label id=".LIST"><p>
2618 Enable output to the listing. The command must be followed by a boolean
2619 switch ("on", "off", "+" or "-") and will enable or disable listing
2621 The option has no effect if the listing is not enabled by the command line
2622 switch -l. If -l is used, an internal counter is set to 1. Lines are output
2623 to the listing file, if the counter is greater than zero, and suppressed if
2624 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
2630 .list on ; Enable listing output
2634 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
2636 Set, how many bytes are shown in the listing for one source line. The
2637 default is 12, so the listing will show only the first 12 bytes for any
2638 source line that generates more than 12 bytes of code or data.
2639 The directive needs an argument, which is either "unlimited", or an
2640 integer constant in the range 4..255.
2645 .listbytes unlimited ; List all bytes
2646 .listbytes 12 ; List the first 12 bytes
2647 .incbin "data.bin" ; Include large binary file
2651 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
2653 This command may only be used inside a macro definition. It declares a
2654 list of identifiers as local to the macro expansion.
2656 A problem when using macros are labels: Since they don't change their name,
2657 you get a "duplicate symbol" error if the macro is expanded the second time.
2658 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
2659 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
2662 Some other assemblers start a new lexical block inside a macro expansion.
2663 This has some drawbacks however, since that will not allow <em/any/ symbol
2664 to be visible outside a macro, a feature that is sometimes useful. The
2665 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
2666 to address the problem.
2668 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
2672 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
2674 Defines the character that start "cheap" local labels. You may use one
2675 of '@' and '?' as start character. The default is '@'.
2677 Cheap local labels are labels that are visible only between two non
2678 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
2679 using explicit lexical nesting.
2686 Clear: lda #$00 ; Global label
2687 ?Loop: sta Mem,y ; Local label
2691 Sub: ... ; New global label
2692 bne ?Loop ; ERROR: Unknown identifier!
2696 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
2698 Insert a predefined macro package. The command is followed by an
2699 identifier specifying the macro package to insert. Available macro
2703 generic Defines generic macros like add and sub.
2704 longbranch Defines conditional long jump macros.
2705 cbm Defines the scrcode macro
2706 cpu Defines constants for the .CPU variable
2709 Including a macro package twice, or including a macro package that
2710 redefines already existing macros will lead to an error.
2715 .macpack longbranch ; Include macro package
2717 cmp #$20 ; Set condition codes
2718 jne Label ; Jump long on condition
2721 Macro packages are explained in more detail in section <ref
2722 id="macropackages" name="Macro packages">.
2725 <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"><p>
2727 Start a classic macro definition. The command is followed by an identifier
2728 (the macro name) and optionally by a comma separated list of identifiers
2729 that are macro parameters.
2731 See section <ref id="macros" name="Macros">.
2734 <sect1><tt>.ORG</tt><label id=".ORG"><p>
2736 Start a section of absolute code. The command is followed by a constant
2737 expression that gives the new PC counter location for which the code is
2738 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
2741 Please note that you <em/do not need/ this command in most cases. Placing
2742 code at a specific address is the job of the linker, not the assembler, so
2743 there is usually no reason to assemble code to a specific address.
2745 You may not switch segments while inside a section of absolute code.
2750 .org $7FF ; Emit code starting at $7FF
2754 <sect1><tt>.OUT</tt><label id=".OUT"><p>
2756 Output a string to the console without producing an error. This command
2757 is similiar to <tt/.ERROR/, however, it does not force an assembler error
2758 that prevents the creation of an object file.
2763 .out "This code was written by the codebuster(tm)"
2766 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
2767 id=".ERROR" name=".ERROR"></tt> directives.
2770 <sect1><tt>.P02</tt><label id=".P02"><p>
2772 Enable the 6502 instruction set, disable 65SC02, 65C02 and 65816
2773 instructions. This is the default if not overridden by the
2774 <tt><ref id="option--cpu" name="--cpu"></tt> command line option.
2776 See: <tt><ref id=".PC02" name=".PC02"></tt>, <tt><ref id=".PSC02"
2777 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2780 <sect1><tt>.P816</tt><label id=".P816"><p>
2782 Enable the 65816 instruction set. This is a superset of the 65SC02 and
2783 6502 instruction sets.
2785 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
2786 name=".PSC02"></tt> and <tt><ref id=".PC02" name=".PC02"></tt>
2789 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
2791 Set the page length for the listing. Must be followed by an integer
2792 constant. The value may be "unlimited", or in the range 32 to 127. The
2793 statement has no effect if no listing is generated. The default value is -1
2794 (unlimited) but may be overridden by the <tt/--pagelength/ command line
2795 option. Beware: Since ca65 is a one pass assembler, the listing is generated
2796 after assembly is complete, you cannot use multiple line lengths with one
2797 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
2802 .pagelength 66 ; Use 66 lines per listing page
2804 .pagelength unlimited ; Unlimited page length
2808 <sect1><tt>.PC02</tt><label id=".PC02"><p>
2810 Enable the 65C02 instructions set. This instruction set includes all
2811 6502 and 65SC02 instructions.
2813 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
2814 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2817 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
2819 Pop the last pushed segment from the stack, and set it.
2821 This command will switch back to the segment that was last pushed onto the
2822 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
2823 command, and remove this entry from the stack.
2825 The assembler will print an error message if the segment stack is empty
2826 when this command is issued.
2828 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
2831 <sect1><tt>.PROC</tt><label id=".PROC"><p>
2833 Start a nested lexical level with the given name and adds a symbol with this
2834 name to the enclosing scope. All new symbols from now on are in the local
2835 lexical level and are accessible from outside only via <ref id="scopesyntax"
2836 name="explicit scope specification">. Symbols defined outside this local
2837 level may be accessed as long as their names are not used for new symbols
2838 inside the level. Symbols names in other lexical levels do not clash, so you
2839 may use the same names for identifiers. The lexical level ends when the
2840 <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read. Lexical levels
2841 may be nested up to a depth of 16 (this is an artificial limit to protect
2842 against errors in the source).
2844 Note: Macro names are always in the global level and in a separate name
2845 space. There is no special reason for this, it's just that I've never
2846 had any need for local macro definitions.
2851 .proc Clear ; Define Clear subroutine, start new level
2853 L1: sta Mem,y ; L1 is local and does not cause a
2854 ; duplicate symbol error if used in other
2857 bne L1 ; Reference local symbol
2859 .endproc ; Leave lexical level
2862 See: <tt/<ref id=".ENDPROC" name=".ENDPROC">/ and <tt/<ref id=".SCOPE"
2866 <sect1><tt>.PSC02</tt><label id=".PSC02"><p>
2868 Enable the 65SC02 instructions set. This instruction set includes all
2871 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PC02"
2872 name=".PC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2875 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
2877 Push the currently active segment onto a stack. The entries on the stack
2878 include the name of the segment and the segment type. The stack has a size
2881 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
2882 to switch to another segment and to restore the old segment later, without
2883 even knowing the name and type of the current segment.
2885 The assembler will print an error message if the segment stack is already
2886 full, when this command is issued.
2888 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
2891 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
2893 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
2894 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
2895 a constant expression that tells how many times the commands in the body
2896 should get repeated. Optionally, a comma and an identifier may be specified.
2897 If this identifier is found in the body of the repeat statement, it is
2898 replaced by the current repeat count (starting with zero for the first time
2899 the body is repeated).
2901 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
2902 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
2903 level will be used, not the one from the outer level.
2907 The following macro will emit a string that is "encrypted" in that all
2908 characters of the string are XORed by the value $55.
2912 .repeat .strlen(Arg), I
2913 .byte .strat(Arg, I) ^ $55
2918 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
2921 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
2923 Switch back to relocatable mode. See the <tt><ref id=".ORG"
2924 name=".ORG"></tt> command.
2927 <sect1><tt>.RES</tt><label id=".RES"><p>
2929 Reserve storage. The command is followed by one or two constant
2930 expressions. The first one is mandatory and defines, how many bytes of
2931 storage should be defined. The second, optional expression must by a
2932 constant byte value that will be used as value of the data. If there
2933 is no fill value given, the linker will use the value defined in the
2934 linker configuration file (default: zero).
2939 ; Reserve 12 bytes of memory with value $AA
2944 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
2946 Switch to the RODATA segment. The name of the RODATA segment is always
2947 "RODATA", so this is a shortcut for
2953 The RODATA segment is a segment that is used by the compiler for
2954 readonly data like string constants.
2956 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2959 <sect1><tt>.SCOPE</tt><label id=".SCOPE"><p>
2961 Start a nested lexical level with the given name. All new symbols from now
2962 on are in the local lexical level and are accessible from outside only via
2963 <ref id="scopesyntax" name="explicit scope specification">. Symbols defined
2964 outside this local level may be accessed as long as their names are not used
2965 for new symbols inside the level. Symbols names in other lexical levels do
2966 not clash, so you may use the same names for identifiers. The lexical level
2967 ends when the <tt><ref id=".ENDSCOPE" name=".ENDSCOPE"></tt> command is
2968 read. Lexical levels may be nested up to a depth of 16 (this is an
2969 artificial limit to protect against errors in the source).
2971 Note: Macro names are always in the global level and in a separate name
2972 space. There is no special reason for this, it's just that I've never
2973 had any need for local macro definitions.
2978 .scope Error ; Start new scope named Error
2980 File = 1 ; File error
2981 Parse = 2 ; Parse error
2982 .endproc ; Close lexical level
2985 lda #Error::File ; Use symbol from scope Error
2988 See: <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/ and <tt/<ref id=".PROC"
2992 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
2994 Switch to another segment. Code and data is always emitted into a
2995 segment, that is, a named section of data. The default segment is
2996 "CODE". There may be up to 254 different segments per object file
2997 (and up to 65534 per executable). There are shortcut commands for
2998 the most common segments ("CODE", "DATA" and "BSS").
3000 The command is followed by a string containing the segment name (there are
3001 some constraints for the name - as a rule of thumb use only those segment
3002 names that would also be valid identifiers). There may also be an optional
3003 address size separated by a colon. See the section covering <tt/<ref
3004 id="address-sizes" name="address sizes">/ for more information.
3006 The default address size for a segment depends on the memory model specified
3007 on the command line. The default is "absolute", which means that you don't
3008 have to use an address size modifier in most cases.
3010 "absolute" means that the is a segment with 16 bit (absolute) addressing.
3011 That is, the segment will reside somewhere in core memory outside the zero
3012 page. "zeropage" (8 bit) means that the segment will be placed in the zero
3013 page and direct (short) addressing is possible for data in this segment.
3015 Beware: Only labels in a segment with the zeropage attribute are marked
3016 as reachable by short addressing. The `*' (PC counter) operator will
3017 work as in other segments and will create absolute variable values.
3019 Please note that a segment cannot have two different address sizes. A
3020 segment specified as zeropage cannot be declared as being absolute later.
3025 .segment "ROM2" ; Switch to ROM2 segment
3026 .segment "ZP2": zeropage ; New direct segment
3027 .segment "ZP2" ; Ok, will use last attribute
3028 .segment "ZP2": absolute ; Error, redecl mismatch
3031 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
3032 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref
3033 id=".RODATA" name=".RODATA"></tt>
3036 <sect1><tt>.SETCPU</tt><label id=".SETCPU"><p>
3038 Switch the CPU instruction set. The command is followed by a string that
3039 specifies the CPU. Possible values are those that can also be supplied to
3040 the <tt><ref id="option--cpu" name="--cpu"></tt> command line option,
3041 namely: 6502, 6502X, 65SC02, 65C02, 65816 and sunplus. Please note that
3042 support for the sunplus CPU is not available in the freeware version,
3043 because the instruction set of the sunplus CPU is "proprietary and
3046 See: <tt><ref id=".CPU" name=".CPU"></tt>,
3047 <tt><ref id=".IFP02" name=".IFP02"></tt>,
3048 <tt><ref id=".IFP816" name=".IFP816"></tt>,
3049 <tt><ref id=".IFPC02" name=".IFPC02"></tt>,
3050 <tt><ref id=".IFPSC02" name=".IFPSC02"></tt>,
3051 <tt><ref id=".P02" name=".P02"></tt>,
3052 <tt><ref id=".P816" name=".P816"></tt>,
3053 <tt><ref id=".PC02" name=".PC02"></tt>,
3054 <tt><ref id=".PSC02" name=".PSC02"></tt>
3057 <sect1><tt>.SMART</tt><label id=".SMART"><p>
3059 Switch on or off smart mode. The command must be followed by a '+' or
3060 '-' character to switch the option on or off respectively. The default
3061 is off (that is, the assembler doesn't try to be smart), but this
3062 default may be changed by the -s switch on the command line.
3064 In smart mode the assembler will do the following:
3067 <item>Track usage of the <tt/REP/ and <tt/SEP/ instructions in 65816 mode
3068 and update the operand sizes accordingly. If the operand of such an
3069 instruction cannot be evaluated by the assembler (for example, because
3070 the operand is an imported symbol), a warning is issued. Beware: Since
3071 the assembler cannot trace the execution flow this may lead to false
3072 results in some cases. If in doubt, use the <tt/.Inn/ and <tt/.Ann/
3073 instructions to tell the assembler about the current settings.
3074 <item>In 65816 mode, replace a <tt/RTS/ instruction by <tt/RTL/ if it is
3075 used within a procedure declared as <tt/far/, or if the procedure has
3076 no explicit address specification, but it is <tt/far/ because of the
3084 .smart - ; Stop being smart
3087 See: <tt><ref id=".A16" name=".A16"></tt>,
3088 <tt><ref id=".A8" name=".A8"></tt>,
3089 <tt><ref id=".I16" name=".I16"></tt>,
3090 <tt><ref id=".I8" name=".I8"></tt>
3093 <sect1><tt>.STRUCT</tt><label id=".STRUCT"><p>
3095 Starts a struct definition. Structs are covered in a separate section named
3096 <ref id="structs" name=""Structs and unions"">.
3098 See: <tt><ref id=".ENDSTRUCT" name=".ENDSTRUCT"></tt>
3101 <sect1><tt>.SUNPLUS</tt><label id=".SUNPLUS"><p>
3103 Enable the SunPlus instructions set. This command will not work in the
3104 freeware version of the assembler, because the instruction set is
3105 "proprietary and confidential".
3107 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
3108 name=".PSC02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt>, and
3109 <tt><ref id=".P816" name=".P816"></tt>
3112 <sect1><tt>.TAG</tt><label id=".TAG"><p>
3114 Allocate space for a struct or union.
3125 .tag Point ; Allocate 4 bytes
3129 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
3131 Force an assembly warning. The assembler will output a warning message
3132 preceeded by "User warning". This warning will always be output, even if
3133 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
3134 command line option.
3136 This command may be used to output possible problems when assembling
3145 .warning "Forward jump in jne, cannot optimize!"
3155 See also the <tt><ref id=".ERROR" name=".ERROR"></tt> and <tt><ref id=".OUT"
3156 name=".OUT"></tt> directives.
3159 <sect1><tt>.WORD</tt><label id=".WORD"><p>
3161 Define word sized data. Must be followed by a sequence of (word ranged,
3162 but not necessarily constant) expressions.
3167 .word $0D00, $AF13, _Clear
3171 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
3173 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
3174 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
3178 .segment "ZEROPAGE", zeropage
3181 Because of the "zeropage" attribute, labels declared in this segment are
3182 addressed using direct addressing mode if possible. You <em/must/ instruct
3183 the linker to place this segment somewhere in the address range 0..$FF
3184 otherwise you will get errors.
3186 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
3190 <sect>Macros<label id="macros"><p>
3193 <sect1>Introduction<p>
3195 Macros may be thought of as "parametrized super instructions". Macros are
3196 sequences of tokens that have a name. If that name is used in the source
3197 file, the macro is "expanded", that is, it is replaced by the tokens that
3198 were specified when the macro was defined.
3201 <sect1>Macros without parameters<p>
3203 In it's simplest form, a macro does not have parameters. Here's an
3207 .macro asr ; Arithmetic shift right
3208 cmp #$80 ; Put bit 7 into carry
3209 ror ; Rotate right with carry
3213 The macro above consists of two real instructions, that are inserted into
3214 the code, whenever the macro is expanded. Macro expansion is simply done
3215 by using the name, like this:
3224 <sect1>Parametrized macros<p>
3226 When using macro parameters, macros can be even more useful:
3240 When calling the macro, you may give a parameter, and each occurence of
3241 the name "addr" in the macro definition will be replaced by the given
3260 A macro may have more than one parameter, in this case, the parameters
3261 are separated by commas. You are free to give less parameters than the
3262 macro actually takes in the definition. You may also leave intermediate
3263 parameters empty. Empty parameters are replaced by empty space (that is,
3264 they are removed when the macro is exanded). If you have a look at our
3265 macro definition above, you will see, that replacing the "addr" parameter
3266 by nothing will lead to wrong code in most lines. To help you, writing
3267 macros with a variable parameter list, there are some control commands:
3269 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
3270 returns true, if there are any tokens on the remainder of the line. Since
3271 empty parameters are replaced by nothing, this may be used to test if a given
3272 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
3275 Look at this example:
3278 .macro ldaxy a, x, y
3291 This macro may be called as follows:
3294 ldaxy 1, 2, 3 ; Load all three registers
3296 ldaxy 1, , 3 ; Load only a and y
3298 ldaxy , , 3 ; Load y only
3301 There's another helper command for determining, which macro parameters are
3302 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is
3303 replaced by the parameter count given, <em/including/ intermediate empty macro
3307 ldaxy 1 ; .PARAMCOUNT = 1
3308 ldaxy 1,,3 ; .PARAMCOUNT = 3
3309 ldaxy 1,2 ; .PARAMCOUNT = 2
3310 ldaxy 1, ; .PARAMCOUNT = 2
3311 ldaxy 1,2,3 ; .PARAMCOUNT = 3
3314 Macro parameters may optionally be enclosed into curly braces. This allows the
3315 inclusion of tokens that would otherwise terminate the parameter (the comma in
3316 case of a macro parameter).
3319 .macro foo arg1, arg2
3323 foo ($00,x) ; Two parameters passed
3324 foo {($00,x)} ; One parameter passed
3327 In the first case, the macro is called with two parameters: '<tt/($00/'
3328 and 'x)'. The comma is not passed to the macro, since it is part of the
3329 calling sequence, not the parameters.
3331 In the second case, '($00,x)' is passed to the macro, this time
3332 including the comma.
3335 <sect1>Detecting parameter types<p>
3337 Sometimes it is nice to write a macro that acts differently depending on the
3338 type of the argument supplied. An example would be a macro that loads a 16 bit
3339 value from either an immediate operand, or from memory. The <tt/<ref
3340 id=".MATCH" name=".MATCH">/ and <tt/<ref id=".XMATCH" name=".XMATCH">/
3341 functions will allow you to do exactly this:
3345 .if (.match (.left (1, {arg}), #))
3347 lda #<(.right (.tcount ({arg})-1, {arg}))
3348 ldx #>(.right (.tcount ({arg})-1, {arg}))
3350 ; assume absolute or zero page
3357 Using the <tt/<ref id=".MATCH" name=".MATCH">/ function, the macro is able to
3358 check if its argument begins with a hash mark. If so, two immediate loads are
3359 emitted, Otherwise a load from an absolute zero page memory location is
3360 assumed. Please note how the curly braces are used to enclose parameters to
3361 pseudo functions handling token lists. This is necessary, because the token
3362 lists may include commas or parens, which would be treated by the assembler
3365 The macro can be used as
3370 ldax #$1234 ; X=$12, A=$34
3372 ldax foo ; X=$56, A=$78
3376 <sect1>Recursive macros<p>
3378 Macros may be used recursively:
3381 .macro push r1, r2, r3
3390 There's also a special macro to help writing recursive macros: <tt><ref
3391 id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion
3395 .macro push r1, r2, r3, r4, r5, r6, r7
3397 ; First parameter is empty
3403 push r2, r3, r4, r5, r6, r7
3407 When expanding this macro, the expansion will push all given parameters
3408 until an empty one is encountered. The macro may be called like this:
3411 push $20, $21, $32 ; Push 3 ZP locations
3412 push $21 ; Push one ZP location
3416 <sect1>Local symbols inside macros<p>
3418 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
3419 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
3420 Have a look at the inc16 macro above. Here is it again:
3434 If you have a closer look at the code, you will notice, that it could be
3435 written more efficiently, like this:
3446 But imagine what happens, if you use this macro twice? Since the label
3447 "Skip" has the same name both times, you get a "duplicate symbol" error.
3448 Without a way to circumvent this problem, macros are not as useful, as
3449 they could be. One solution is, to start a new lexical block inside the
3463 Now the label is local to the block and not visible outside. However,
3464 sometimes you want a label inside the macro to be visible outside. To make
3465 that possible, there's a new command that's only usable inside a macro
3466 definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one
3467 or more symbols as local to the macro expansion. The names of local variables
3468 are replaced by a unique name in each separate macro expansion. So we could
3469 also solve the problem above by using <tt/.LOCAL/:
3473 .local Skip ; Make Skip a local symbol
3480 Skip: ; Not visible outside
3485 <sect1>C style macros<p>
3487 Starting with version 2.5 of the assembler, there is a second macro type
3488 available: C style macros using the <tt/.DEFINE/ directive. These macros are
3489 similar to the classic macro type described above, but behaviour is sometimes
3494 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
3495 span more than a line. You may use line continuation (see <tt><ref
3496 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
3497 more than one line for increased readability, but the macro itself
3498 may not contain an end-of-line token.
3500 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
3501 the name space with classic macros, but they are detected and replaced
3502 at the scanner level. While classic macros may be used in every place,
3503 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
3504 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
3505 they are more versatile in some situations.
3507 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
3508 parameters. While classic macros may have empty parameters, this is
3509 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
3510 For this macro type, the number of actual parameters must match
3511 exactly the number of formal parameters.
3513 To make this possible, formal parameters are enclosed in braces when
3514 defining the macro. If there are no parameters, the empty braces may
3517 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
3518 contain end-of-line tokens, there are things that cannot be done. They
3519 may not contain several processor instructions for example. So, while
3520 some things may be done with both macro types, each type has special
3521 usages. The types complement each other.
3525 Let's look at a few examples to make the advantages and disadvantages
3528 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
3529 following <tt/.DEFINE/:
3534 foo EQU $1234 ; This is accepted now
3537 You may use the directive to define string constants used elsewhere:
3540 ; Define the version number
3541 .define VERSION "12.3a"
3547 Macros with parameters may also be useful:
3550 .define DEBUG(message) .out message
3552 DEBUG "Assembling include file #3"
3555 Note that, while formal parameters have to be placed in braces, this is
3556 not true for the actual parameters. Beware: Since the assembler cannot
3557 detect the end of one parameter, only the first token is used. If you
3558 don't like that, use classic macros instead:
3566 (This is an example where a problem can be solved with both macro types).
3569 <sect1>Characters in macros<p>
3571 When using the <ref id="option-t" name="-t"> option, characters are translated
3572 into the target character set of the specific machine. However, this happens
3573 as late as possible. This means that strings are translated if they are part
3574 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
3575 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
3576 used as part of an expression.
3578 This behaviour is very intuitive outside of macros but may be confusing when
3579 doing more complex macros. If you compare characters against numeric values,
3580 be sure to take the translation into account.
3585 <sect>Macro packages<label id="macropackages"><p>
3587 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
3588 macro packages may be included with just one command. Available macro packages
3592 <sect1><tt>.MACPACK generic</tt><p>
3594 This macro package defines macros that are useful in almost any program.
3595 Currently, two macros are defined:
3610 <sect1><tt>.MACPACK longbranch</tt><p>
3612 This macro package defines long conditional jumps. They are named like the
3613 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
3614 definition for the "<tt/jeq/" macro, the other macros are built using the same
3619 .if .def(Target) .and ((*+2)-(Target) <= 127)
3628 All macros expand to a short branch, if the label is already defined (back
3629 jump) and is reachable with a short jump. Otherwise the macro expands to a
3630 conditional branch with the branch condition inverted, followed by an absolute
3631 jump to the actual branch target.
3633 The package defines the following macros:
3636 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
3641 <sect1><tt>.MACPACK cbm</tt><p>
3643 The cbm macro package will define a macro named <tt/scrcode/. It takes a
3644 string as argument and places this string into memory translated into screen
3648 <sect1><tt>.MACPACK cpu</tt><p>
3650 This macro package does not define any macros but constants used to examine
3651 the value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable. For
3652 each supported CPU a constant similar to
3663 is defined. These constants may be used to determine the exact type of the
3664 currently enabled CPU. In addition to that, for each CPU instruction set,
3665 another constant is defined:
3676 The value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable may
3677 be checked with <tt/<ref id="operators" name=".BITAND">/ to determine if the
3678 currently enabled CPU supports a specific instruction set. For example the
3679 65C02 supports all instructions of the 65SC02 CPU, so it has the
3680 <tt/CPU_ISET_65SC02/ bit set in addition to its native <tt/CPU_ISET_65C02/
3684 .if (.cpu .bitand CPU_ISET_65SC02)
3692 it is possible to determine if the
3698 instruction is supported, which is the case for the 65SC02, 65C02 and 65816
3699 CPUs (the latter two are upwards compatible to the 65SC02).
3703 <sect>Predefined constants<label id="predefined-constants"><p>
3705 For better orthogonality, the assembler defines similar symbols as the
3706 compiler, depending on the target system selected:
3709 <item><tt/__ACE__/ - Target system is <tt/ace/
3710 <item><tt/__APPLE2__",/ - Target system is <tt/apple2/
3711 <item><tt/__APPLE2ENH__",/ - Target system is <tt/apple2enh/
3712 <item><tt/__ATARI__/ - Target system is <tt/atari/
3713 <item><tt/__ATMOS__",/ - Target system is <tt/atmos/
3714 <item><tt/__BBC__",/ - Target system is <tt/bbc/
3715 <item><tt/__C128__/ - Target system is <tt/c128/
3716 <item><tt/__C16__/ - Target system is <tt/c16/
3717 <item><tt/__C64__/ - Target system is <tt/c64/
3718 <item><tt/__CBM__/ - Target is a Commodore system
3719 <item><tt/__CBM510__/ - Target system is <tt/cbm510/
3720 <item><tt/__CBM610__/ - Target system is <tt/cbm610/
3721 <item><tt/__GEOS__",/ - Target system is <tt/geos/
3722 <item><tt/__LUNIX__",/ - Target system is <tt/lunix/
3723 <item><tt/__NES__",/ - Target system is <tt/nes/
3724 <item><tt/__PET__/ - Target system is <tt/pet/
3725 <item><tt/__PLUS4__/ - Target system is <tt/plus4/
3726 <item><tt/__SUPERVISION__",/ - Target system is <tt/supervision/
3727 <item><tt/__VIC20__/ - Target system is <tt/vic20/
3731 <sect>Structs and unions<label id="structs"><p>
3733 Structs and unions are special forms of <ref id="scopes" name="scopes">. They
3734 are to some degree comparable to their C counterparts. Both have a list of
3735 members. Each member allocates storage and may optionally have a name, which,
3736 in case of a struct, is the offset from the beginning and, in case of a union,
3739 Here is an example for a very simple struct with two members and a total size
3749 A union shares the total space between all its members, its size is the same
3750 as that of the largest member.
3752 A struct or union must not necessarily have a name. If it is anonymous, no
3753 local scope is opened, the identifiers used to name the members are placed
3754 into the current scope instead.
3756 A struct may contain unnamed members and definitions of local structs. The
3757 storage allocators may contain a multiplier, as in the example below:
3762 .word 2 ; Allocate two words
3768 Using the <ref id=".TAG" name=".TAG"> keyword, it is possible to embedd
3769 already defined structs or unions in structs:
3783 Space for a struct or union may be allocated using the <ref id=".TAG"
3784 name=".TAG"> directive.
3790 Currently, members are just offsets from the start of the struct or union. To
3791 access a field of a struct, the member offset has to be added to the address
3792 of the struct itself:
3795 lda C+Circle::Radius ; Load circle radius into A
3798 This may change in a future version of the assembler.
3801 <sect>Module constructors/destructors<label id="condes"><p>
3803 <em>Note:</em> This section applies mostly to C programs, so the explanation
3804 below uses examples from the C libraries. However, the feature may also be
3805 useful for assembler programs.
3810 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
3811 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
3812 name=".INTERRUPTOR"></tt>keywords it it possible to export functions in a
3813 special way. The linker is able to generate tables with all functions of a
3814 specific type. Such a table will <em>only</em> include symbols from object
3815 files that are linked into a specific executable. This may be used to add
3816 initialization and cleanup code for library modules, or a table of interrupt
3819 The C heap functions are an example where module initialization code is used.
3820 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
3821 variables that contain the start and the end of the heap, pointers to the free
3822 list and so on. Since the end of the heap depends on the size and start of the
3823 stack, it must be initialized at runtime. However, initializing these
3824 variables for programs that do not use the heap are a waste of time and
3827 So the central module defines a function that contains initialization code and
3828 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
3829 this module is added to an executable by the linker, the initialization
3830 function will be placed into the table of constructors by the linker. The C
3831 startup code will call all constructors before <tt/main/ and all destructors
3832 after <tt/main/, so without any further work, the heap initialization code is
3833 called once the module is linked in.
3835 While it would be possible to add explicit calls to initialization functions
3836 in the startup code, the new approach has several advantages:
3840 If a module is not included, the initialization code is not linked in and not
3841 called. So you don't pay for things you don't need.
3844 Adding another library that needs initialization does not mean that the
3845 startup code has to be changed. Before we had module constructors and
3846 destructors, the startup code for all systems had to be adjusted to call the
3847 new initialization code.
3850 The feature saves memory: Each additional initialization function needs just
3851 two bytes in the table (a pointer to the function).
3856 <sect1>Calling order<p>
3858 The symbols are sorted in increasing priority order by the linker when using
3859 one of the builtin linker configurations, so the functions with lower
3860 priorities come first and are followed by those with higher priorities. The C
3861 library runtime subroutine that walks over the function tables calls the
3862 functions starting from the top of the table - which means that functions with
3863 a high priority are called first.
3865 So when using the C runtime, functions are called with high priority functions
3866 first, followed by low priority functions.
3871 When using these special symbols, please take care of the following:
3876 The linker will only generate function tables, it will not generate code to
3877 call these functions. If you're using the feature in some other than the
3878 existing C environments, you have to write code to call all functions in a
3879 linker generated table yourself. See the <tt/condes/ and <tt/callirq/ modules
3880 in the C runtime for an example on how to do this.
3883 The linker will only add addresses of functions that are in modules linked to
3884 the executable. This means that you have to be careful where to place the
3885 condes functions. If initialization or an irq handler is needed for a group of
3886 functions, be sure to place the function into a module that is linked in
3887 regardless of which function is called by the user.
3890 The linker will generate the tables only when requested to do so by the
3891 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
3892 be requested separately.
3895 Constructors and destructors may have priorities. These priorities determine
3896 the order of the functions in the table. If your intialization or cleanup code
3897 does depend on other initialization or cleanup code, you have to choose the
3898 priority for the functions accordingly.
3901 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt>, <tt><ref
3902 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> and <tt><ref id=".INTERRUPTOR"
3903 name=".INTERRUPTOR"></tt>statements, there is also a more generic command:
3904 <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to specify an
3905 additional type. Predefined types are 0 (constructor), 1 (destructor) and 2
3906 (interruptor). The linker generates a separate table for each type on request.
3911 <sect>Porting sources from other assemblers<p>
3913 Sometimes it is necessary to port code written for older assemblers to ca65.
3914 In some cases, this can be done without any changes to the source code by
3915 using the emulation features of ca65 (see <tt><ref id=".FEATURE"
3916 name=".FEATURE"></tt>). In other cases, it is necessary to make changes to the
3919 Probably the biggest difference is the handling of the <tt><ref id=".ORG"
3920 name=".ORG"></tt> directive. ca65 generates relocatable code, and placement is
3921 done by the linker. Most other assemblers generate absolute code, placement is
3922 done within the assembler and there is no external linker.
3924 In general it is not a good idea to write new code using the emulation
3925 features of the assembler, but there may be situations where even this rule is
3930 You need to use some of the ca65 emulation features to simulate the behaviour
3931 of such simple assemblers.
3934 <item>Prepare your sourcecode like this:
3937 ; if you want TASS style labels without colons
3938 .feature labels_without_colons
3940 ; if you want TASS style character constants
3941 ; ("a" instead of the default 'a')
3942 .feature loose_char_term
3944 .word *+2 ; the cbm load address
3949 notice that the two emulation features are mostly useful for porting
3950 sources originally written in/for TASS, they are not needed for the
3951 actual "simple assembler operation" and are not recommended if you are
3952 writing new code from scratch.
3954 <item>Replace all program counter assignments (which are not possible in ca65
3955 by default, and the respective emulation feature works different from what
3956 you'd expect) by another way to skip to another memory location, for example
3957 the <tt><ref id=".RES" name=".RES"></tt>directive.
3961 .res $2000-* ; reserve memory up to $2000
3964 notice that other than the original TASS, ca65 can never move the
3965 programmcounter backwards - think of it as if you are assembling to disc with
3968 <item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.goto/ etc.) must be
3969 rewritten to match ca65 syntax. Most importantly notice that due to the lack
3970 of <tt/.goto/, everything involving loops must be replaced by
3971 <tt><ref id=".REPEAT" name=".REPEAT"></tt>.
3973 <item>To assemble code to a different address than it is executed at, use the
3974 <tt><ref id=".ORG" name=".ORG"></tt> directive instead of
3975 <tt/.offs/-constructs.
3982 .reloc ; back to normal
3985 <item>Then assemble like this:
3988 cl65 --start-addr 0x0ffe -t none myprog.s -o myprog.prg
3991 notice that you need to use the actual start address minus two, since two
3992 bytes are used for the cbm load address.
3997 <sect>Bugs/Feedback<p>
3999 If you have problems using the assembler, if you find any bugs, or if
4000 you're doing something interesting with the assembler, I would be glad to
4001 hear from you. Feel free to contact me by email
4002 (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
4008 ca65 (and all cc65 binutils) are (C) Copyright 1998-2003 Ullrich von
4009 Bassewitz. For usage of the binaries and/or sources the following
4010 conditions do apply:
4012 This software is provided 'as-is', without any expressed or implied
4013 warranty. In no event will the authors be held liable for any damages
4014 arising from the use of this software.
4016 Permission is granted to anyone to use this software for any purpose,
4017 including commercial applications, and to alter it and redistribute it
4018 freely, subject to the following restrictions:
4021 <item> The origin of this software must not be misrepresented; you must not
4022 claim that you wrote the original software. If you use this software
4023 in a product, an acknowledgment in the product documentation would be
4024 appreciated but is not required.
4025 <item> Altered source versions must be plainly marked as such, and must not
4026 be misrepresented as being the original software.
4027 <item> This notice may not be removed or altered from any source