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 --listing Create a listing if assembly was ok
113 --pagelength n Set the page length for the listing
114 --smart Enable smart mode
115 --target sys Set the target system
116 --verbose Increase verbosity
117 --version Print the assembler version
118 ---------------------------------------------------------------------------
122 <sect1>Command line options in detail<p>
124 Here is a description of all the command line options:
128 <label id="option--cpu">
129 <tag><tt>--cpu type</tt></tag>
131 Set the default for the CPU type. The option takes a parameter, which
134 6502, 65SC02, 65C02, 65816 and sunplus
136 The last one (sunplus) is not available in the freeware version, because the
137 instruction set of the sunplus CPU is "proprietary and confidential".
140 <label id="option--feature">
141 <tag><tt>--feature name</tt></tag>
143 Enable an emulation feature. This is identical as using <tt/.FEATURE/
144 in the source with two exceptions: Feature names must be lower case, and
145 each feature must be specified by using an extra <tt/--feature/ option,
146 comma separated lists are not allowed.
148 See the discussion of the <tt><ref id=".FEATURE" name=".FEATURE"></tt>
149 command for a list of emulation features.
152 <label id="option-g">
153 <tag><tt>-g, --debug-info</tt></tag>
155 When this option (or the equivalent control command <tt/.DEBUGINFO/) is
156 used, the assembler will add a section to the object file that contains
157 all symbols (including local ones) together with the symbol values and
158 source file positions. The linker will put these additional symbols into
159 the VICE label file, so even local symbols can be seen in the VICE
163 <tag><tt>-h, --help</tt></tag>
165 Print the short option summary shown above.
168 <tag><tt>-i, --ignore-case</tt></tag>
170 This option makes the assembler case insensitive on identifiers and labels.
171 This option will override the default, but may itself be overriden by the
172 <tt><ref id=".CASE" name=".CASE"></tt> control command.
175 <tag><tt>-l, --listing</tt></tag>
177 Generate an assembler listing. The listing file will always have the
178 name of the main input file with the extension replaced by ".lst". This
179 may change in future versions.
182 <tag><tt>-o name</tt></tag>
184 The default output name is the name of the input file with the extension
185 replaced by ".o". If you don't like that, you may give another name with
186 the -o option. The output file will be placed in the same directory as
187 the source file, or, if -o is given, the full path in this name is used.
190 <tag><tt>--pagelength n</tt></tag>
192 sets the length of a listing page in lines. See the <tt><ref
193 id=".PAGELENGTH" name=".PAGELENGTH"></tt> directive for more information.
196 <tag><tt>-s, --smart-mode</tt></tag>
198 In smart mode (enabled by -s or the <tt><ref id=".SMART" name=".SMART"></tt>
199 pseudo instruction) the assembler will track usage of the <tt/REP/ and
200 <tt/SEP/ instructions in 65816 mode and update the operand sizes
201 accordingly. If the operand of such an instruction cannot be evaluated by
202 the assembler (for example, because the operand is an imported symbol), a
205 Beware: Since the assembler cannot trace the execution flow this may
206 lead to false results in some cases. If in doubt, use the .ixx and .axx
207 instructions to tell the assembler about the current settings. Smart
208 mode is off by default.
211 <label id="option-t">
212 <tag><tt>-t sys, --target sys</tt></tag>
214 Set the target system. This will enable translation of character strings
215 and character constants into the character set of the target platform.
216 The default for the target system is "none", which means that no translation
217 will take place. The assembler supports the same target systems as the
218 compiler, see there for a list.
221 <tag><tt>-v, --verbose</tt></tag>
223 Increase the assembler verbosity. Usually only needed for debugging
224 purposes. You may use this option more than one time for even more
228 <tag><tt>-D</tt></tag>
230 This option allows you to define symbols on the command line. Without a
231 value, the symbol is defined with the value zero. When giving a value,
232 you may use the '$' prefix for hexadecimal symbols. Please note
233 that for some operating systems, '$' has a special meaning, so
234 you may have to quote the expression.
237 <tag><tt>-I dir, --include-dir dir</tt></tag>
239 Name a directory which is searched for include files. The option may be
240 used more than once to specify more than one directory to search. The
241 current directory is always searched first before considering any
242 additional directores.
245 <tag><tt>-U, --auto-import</tt></tag>
247 Mark symbols that are not defined in the sources as imported symbols. This
248 should be used with care since it delays error messages about typos and such
249 until the linker is run. The compiler uses the equivalent of this switch
250 (<tt><ref id=".AUTOIMPORT" name=".AUTOIMPORT"></tt>) to enable auto imported
251 symbols for the runtime library. However, the compiler is supposed to
252 generate code that runs through the assembler without problems, something
253 which is not always true for assembler programmers.
256 <tag><tt>-V, --version</tt></tag>
258 Print the version number of the assembler. If you send any suggestions
259 or bugfixes, please include the version number.
262 <label id="option-W">
263 <tag><tt>-Wn</tt></tag>
265 Set the warning level for the assembler. Using -W2 the assembler will
266 even warn about such things like unused imported symbols. The default
267 warning level is 1, and it would probably be silly to set it to
274 <sect>Input format<p>
276 <sect1>Assembler syntax<p>
278 The assembler accepts the standard 6502/65816 assembler syntax. One line may
279 contain a label (which is identified by a colon), and, in addition to the
280 label, an assembler mnemonic, a macro, or a control command (see section <ref
281 id="control-commands" name="Control Commands"> for supported control
282 commands). Alternatively, the line may contain a symbol definition using the
283 '=' token. Everything after a semicolon is handled as a comment (that is, it
286 Here are some examples for valid input lines:
289 Label: ; A label and a comment
290 lda #$20 ; A 6502 instruction plus comment
291 L1: ldx #$20 ; Same with label
292 L2: .byte "Hello world" ; Label plus control command
293 mymac $20 ; Macro expansion
294 MySym = 3*L1 ; Symbol definition
295 MaSym = Label ; Another symbol
298 The assembler accepts
301 <item>all valid 6502 mnemonics when in 6502 mode (the default or after the
302 <tt><ref id=".P02" name=".P02"></tt> command was given).
303 <item>all valid 65SC02 mnemonics when in 65SC02 mode (after the
304 <tt><ref id=".PSC02" name=".PSC02"></tt> command was given).
305 <item>all valid 65C02 mnemonics when in 65C02 mode (after the
306 <tt><ref id=".PC02" name=".PC02"></tt> command was given).
307 <item>all valid 65618 mnemonics when in 65816 mode (after the
308 <tt><ref id=".P816" name=".P816"></tt> command was given).
309 <item>all valid SunPlus mnemonics when in SunPlus mode (after the
310 <tt><ref id=".SUNPLUS" name=".SUNPLUS"></tt> command was given).
316 In 65816 mode several aliases are accepted in addition to the official
320 BGE is an alias for BCS
321 BLT is an alias for BCC
322 CPA is an alias for CMP
323 DEA is an alias for DEC A
324 INA is an alias for INC A
325 SWA is an alias for XBA
326 TAD is an alias for TCD
327 TAS is an alias for TCS
328 TDA is an alias for TDC
329 TSA is an alias for TSC
332 Evaluation of banked expressions in 65816 mode differs slightly from the
335 Instead of accepting a 24 bit address (something that is difficult for
336 the assembler to determine and would have required one more special
337 .import command), the bank and the absolute address in that bank are
341 jsl 3.$1234 ; Call subroutine at $1234 in bank 3
344 <sect1>Number format<p>
346 For literal values, the assembler accepts the widely used number formats:
347 A preceeding '$' denotes a hex value, a preceeding '%' denotes a
348 binary value, and a bare number is interpeted as a decimal. There are
349 currently no octal values and no floats.
352 <sect1>Conditional assembly<p>
354 Please note that when using the conditional directives (<tt/.IF/ and friends),
355 the input must consist of valid assembler tokens, even in <tt/.IF/ branches
356 that are not assembled. The reason for this behaviour is that the assembler
357 must still be able to detect the ending tokens (like <tt/.ENDIF/), so
358 conversion of the input stream into tokens still takes place. As a consequence
359 conditional assembly directives may <bf/not/ be used to prevent normal text
360 (used as a comment or similar) from being assembled. <p>
366 <sect1>Expression evaluation<p>
368 All expressions are evaluated with (at least) 32 bit precision. An
369 expression may contain constant values and any combination of internal and
370 external symbols. Expressions that cannot be evaluated at assembly time
371 are stored inside the object file for evaluation by the linker.
372 Expressions referencing imported symbols must always be evaluated by the
376 <sect1>Size of an expression result<p>
378 Sometimes, the assembler must know about the size of the value that is the
379 result of an expression. This is usually the case, if a decision has to be
380 made, to generate a zero page or an absolute memory references. In this
381 case, the assembler has to make some assumptions about the result of an
385 <item> If the result of an expression is constant, the actual value is
386 checked to see if it's a byte sized expression or not.
387 <item> If the expression is explicitly casted to a byte sized expression by
388 one of the '>', '<' or '^' operators, it is a byte expression.
389 <item> If this is not the case, and the expression contains a symbol,
390 explicitly declared as zero page symbol (by one of the .importzp or
391 .exportzp instructions), then the whole expression is assumed to be
393 <item> If the expression contains symbols that are not defined, and these
394 symbols are local symbols, the enclosing scopes are searched for a
395 symbol with the same name. If one exists and this symbol is defined,
396 it's attributes are used to determine the result size.
397 <item> In all other cases the expression is assumed to be word sized.
400 Note: If the assembler is not able to evaluate the expression at assembly
401 time, the linker will evaluate it and check for range errors as soon as
405 <sect1>Boolean expressions<p>
407 In the context of a boolean expression, any non zero value is evaluated as
408 true, any other value to false. The result of a boolean expression is 1 if
409 it's true, and zero if it's false. There are boolean operators with extrem
410 low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/
411 operators are shortcut operators. That is, if the result of the expression is
412 already known, after evaluating the left hand side, the right hand side is
416 <sect1>Constant expressions<p>
418 Sometimes an expression must evaluate to a constant without looking at any
419 further input. One such example is the <tt/<ref id=".IF" name=".IF">/ command
420 that decides if parts of the code are assembled or not. An expression used in
421 the <tt/.IF/ command cannot reference a symbol defined later, because the
422 decision about the <tt/.IF/ must be made at the point when it is read. If the
423 expression used in such a context contains only constant numerical values,
424 there is no problem. When unresolvable symbols are involved it may get harder
425 for the assembler to determine if the expression is actually constant, and it
426 is even possible to create expressions that aren't recognized as constant.
427 Simplifying the expressions will often help.
429 In cases where the result of the expression is not needed immediately, the
430 assembler will delay evaluation until all input is read, at which point all
431 symbols are known. So using arbitrary complex constant expressions is no
432 problem in most cases.
436 <sect1>Available operators<label id="operators"><p>
438 Available operators sorted by precedence:
441 Op Description Precedence
442 -------------------------------------------------------------------
443 Builtin string functions 0
445 Builtin pseudo variables 1
446 Builtin pseudo functions 1
449 ~ Unary bitwise not 1
450 .BITNOT Unary bitwise not 1
451 < Low byte operator 1
452 > High byte operator 1
453 ^ Bank byte operator 1
457 .MOD Modulo operation 2
459 .BITAND Bitwise and 2
461 .BITXOR Bitwise xor 2
462 << Shift left operator 2
463 .SHL Shift left operator 2
464 >> Shift right operator
465 .SHR Shift right operator 2
472 = Compare operation (equal) 4
473 <> Compare operation (not equal) 4
474 < Compare operation (less) 4
475 > Compare operation (greater) 4
476 <= Compare operation (less or equal) 4
477 >= Compare operation (greater or equal) 4
479 && Boolean and 5
491 To force a specific order of evaluation, braces may be used as usual.
497 <sect>Symbols and labels<p>
499 The assembler allows you to use symbols instead of naked values to make
500 the source more readable. There are a lot of different ways to define and
501 use symbols and labels, giving a lot of flexibility.
504 <sect1>Numeric constants<p>
506 Numeric constants are defined using the equal sign or the label assignment
507 operator. After doing
513 may use the symbol "two" in every place where a number is expected, and it is
514 evaluated to the value 2 in this context. The label assignment operator causes
515 the same, but causes the symbol to be marked as a label, which may cause a
516 different handling in the debugger:
522 The right side can of course be an expression:
529 <sect1>Standard labels<p>
531 A label is defined by writing the name of the label at the start of the line
532 (before any instruction mnemonic, macro or pseudo directive), followed by a
533 colon. This will declare a symbol with the given name and the value of the
534 current program counter.
537 <sect1>Local labels and symbols<p>
539 Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to
540 create regions of code where the names of labels and symbols are local to this
541 region. They are not known outside of this region and cannot be accessed from
542 there. Such regions may be nested like PROCEDUREs in Pascal.
544 See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
545 directive for more information.
548 <sect1>Cheap local labels<p>
550 Cheap local labels are defined like standard labels, but the name of the
551 label must begin with a special symbol (usually '@', but this can be
552 changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt>
555 Cheap local labels are visible only between two non cheap labels. As soon as a
556 standard symbol is encountered (this may also be a local symbol if inside a
557 region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the
558 cheap local symbol goes out of scope.
560 You may use cheap local labels as an easy way to reuse common label
561 names like "Loop". Here is an example:
564 Clear: lda #$00 ; Global label
566 @Loop: sta Mem,y ; Local label
570 Sub: ... ; New global label
571 bne @Loop ; ERROR: Unknown identifier!
574 <sect1>Unnamed labels<p>
576 If you really want to write messy code, there are also unnamed
577 labels. These labels do not have a name (you guessed that already,
578 didn't you?). A colon is used to mark the absence of the name.
580 Unnamed labels may be accessed by using the colon plus several minus
581 or plus characters as a label designator. Using the '-' characters
582 will create a back reference (use the n'th label backwards), using
583 '+' will create a forward reference (use the n'th label in forward
584 direction). An example will help to understand this:
606 As you can see from the example, unnamed labels will make even short
607 sections of code hard to understand, because you have to count labels
608 to find branch targets (this is the reason why I for my part do
609 prefer the "cheap" local labels). Nevertheless, unnamed labels are
610 convenient in some situations, so it's your decision.
613 <sect1>Using macros to define labels and constants<p>
615 While there are drawbacks with this approach, it may be handy in some
616 situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is
617 possible to define symbols or constants that may be used elsewhere. Since
618 the macro facility works on a very low level, there is no scoping. On the
619 other side, you may also define string constants this way (this is not
620 possible with the other symbol types).
626 .DEFINE version "SOS V2.3"
628 four = two * two ; Ok
631 .PROC ; Start local scope
632 two = 3 ; Will give "2 = 3" - invalid!
637 <sect1>Symbols and <tt>.DEBUGINFO</tt><p>
639 If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref
640 id="option-g" name="-g"> is given on the command line), global, local and
641 cheap local labels are written to the object file and will be available in the
642 symbol file via the linker. Unnamed labels are not written to the object file,
643 because they don't have a name which would allow to access them.
647 <sect>Scopes<label id="scopes"><p>
649 ca65 implements several sorts of scopes for symbols.
651 <sect1>Global scope<p>
653 All (non cheap local) symbols that are declared outside of any nested scopes
657 <sect1>A special scope: cheap locals<p>
659 A special scope is the scope for cheap local symbols. It lasts from one non
660 local symbol to the next one, without any provisions made by the programmer.
661 All other scopes differ in usage but use the same concept internally.
664 <sect1>Generic nested scopes<p>
666 A nested scoped for generic use is started with <tt/<ref id=".SCOPE"
667 name=".SCOPE">/ and closed with <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/.
668 The scope can have a name, in which case it is accessible from the outside by
669 using <ref id="scopesyntax" name="explicit scopes">. If the scope does not
670 have a name, all symbols created within the scope are local to the scope, and
671 aren't accessible from the outside.
673 A nested scope can access symbols from the local or from enclosing scopes by
674 name without using explicit scope names. In some cases there may be
675 ambiguities, for example if there is a reference to a local symbol that is not
676 yet defined, but a symbol with the same name exists in outer scopes:
688 In the example above, the <tt/lda/ instruction will load the value 3 into the
689 accumulator, because <tt/foo/ is redefined in the scope. However:
701 Here, <tt/lda/ will still load from <tt/$12,x/, but since it is unknown to the
702 assembler that <tt/foo/ is a zeropage symbol when translating the instruction,
703 absolute mode is used instead. In fact, the assembler will not use absolute
704 mode by default, but it will search through the enclosing scopes for a symbol
705 with the given name. If one is found, the address size of this symbol is used.
706 This may lead to errors:
718 In this case, when the assembler sees the symbol <tt/foo/ in the <tt/lda/
719 instruction, it will search for an already defined symbol <tt/foo/. It will
720 find <tt/foo/ in scope <tt/outer/, and a close look reveals that it is a
721 zeropage symbol. So the assembler will use zeropage addressing mode. If
722 <tt/foo/ is redefined later in scope <tt/inner/, the assembler tries to change
723 the address in the <tt/lda/ instruction already translated, but since the new
724 value needs absolute addressing mode, this fails, and an error message "Range
727 Of course the most simple solution for the problem is to move the definition
728 of <tt/foo/ in scope <tt/inner/ upwards, so it preceeds its use. There may be
729 rare cases when this cannot be done. In these cases, you can use one of the
730 address size override operators:
742 This will cause the <tt/lda/ instruction to be translated using absolute
743 addressing mode, which means changing the symbol reference later does not
747 <sect1>Nested procedures<p>
749 A nested procedure is created by use of <tt/<ref id=".PROC" name=".PROC">/. It
750 differs from a <tt/<ref id=".SCOPE" name=".SCOPE">/ in that it must have a
751 name, and a it will introduce a symbol with this name in the enclosing scope.
760 is actually the same as
769 This is the reason why a procedure must have a name. If you want a scope
770 without a name, use <tt/<ref id=".SCOPE" name=".SCOPE">/.
772 <bf/Note:/ As you can see from the example above, scopes and symbols live in
773 different namespaces. There can be a symbol named <tt/foo/ and a scope named
774 <tt/foo/ without any conflicts (but see the section titled <ref
775 id="scopesearch" name=""Scope search order"">).
778 <sect1>Structs, unions and enums<p>
780 Structs, unions and enums are explained in a <ref id="structs" name="separate
781 section">, I do only cover them here, because if they are declared with a
782 name, they open a nested scope, similar to <tt/<ref id=".SCOPE"
783 name=".SCOPE">/. However, when no name is specified, the behaviour is
784 different: In this case, no new scope will be opened, symbols declared within
785 a struct, union, or enum declaration will then be added to the enclosing scope
789 <sect1>Explicit scope specification<label id="scopesyntax"><p>
791 Accessing symbols from other scopes is possible by using an explicit scope
792 specification, provided that the scope where the symbol lives in has a name.
793 The namespace token (<tt/::/) is used to access other scopes:
801 lda foo::bar ; Access foo in scope bar
804 The only way to deny access to a scope from the outside is to declare a scope
805 without a name (using the <tt/<ref id=".SCOPE" name=".SCOPE">/ command).
807 A special syntax is used to specify the global scope: If a symbol or scope is
808 preceeded by the namespace token, the global scope is searched:
815 lda #::bar ; Access the global bar (which is 3)
820 <sect1>Scope search order<label id="scopesearch"><p>
822 The assembler searches for a scope in a similar way as for a symbol. First, it
823 looks in the current scope, and then it walks up the enclosing scopes until
826 However, one important thing to note when using explicit scope syntax is, that
827 a symbol may be accessed before it is defined, but a scope may <bf/not/ be
828 used without a preceeding definition. This means that in the following
837 lda #foo::bar ; Will load 3, not 2!
844 the reference to the scope <tt/foo/ will use the global scope, and not the
845 local one, because the local one is not visible at the point where it is
848 Things get more complex if a complete chain of scopes is specified:
859 lda #outer::inner::bar ; 1
871 When <tt/outer::inner::bar/ is referenced in the <tt/lda/ instruction, the
872 assembler will first search in the local scope for a scope named <tt/outer/.
873 Since none is found, the enclosing scope (<tt/another/) is checked. There is
874 still no scope named <tt/outer/, so scope <tt/foo/ is checked, and finally
875 scope <tt/outer/ is found. Within this scope, <tt/inner/ is searched, and in
876 this scope, the assembler looks for a symbol named <tt/bar/.
878 Please note that once the anchor scope is found, all following scopes
879 (<tt/inner/ in this case) are expected to be found exactly in this scope. The
880 assembler will search the scope tree only for the first scope (if it is not
881 anchored in the root scope). Starting from there on, there is no flexibility,
882 so if the scope named <tt/outer/ found by the assembler does not contain a
883 scope named <tt/inner/, this would be an error, even if such a pair does exist
884 (one level up in global scope).
886 Ambiguities that may be introduced by this search algorithm may be removed by
887 anchoring the scope specification in the global scope. In the example above,
888 if you want to access the "other" symbol <tt/bar/, you would have to write:
899 lda #::outer::inner::bar ; 2
912 <sect>Address sizes and memory models<label id="address-sizes"><p>
914 <sect1>Address sizes<p>
916 ca65 assigns each segment and each symbol an address size. This is true, even
917 if the symbol is not used as an address. You may also think of a value range
918 of the symbol instead of an address size.
920 Possible address sizes are:
923 <item>Zeropage or direct (8 bits)
924 <item>Absolute (16 bits)
929 Since the assembler uses default address sizes for the segments and symbols,
930 it is usually not necessary to override the default behaviour. In cases, where
931 it is necessary, the following keywords may be used to specify address sizes:
934 <item>DIRECT, ZEROPAGE or ZP for zeropage addressing (8 bits).
935 <item>ABSOLUTE, ABS or NEAR for absolute addressing (16 bits).
936 <item>FAR for far addressing (24 bits).
937 <item>LONG or DWORD for long addressing (32 bits).
941 <sect1>Address sizes of segments<p>
943 The assembler assigns an address size to each segment. Since the
944 representation of a label within this segment is "segment start + offset",
945 labels will inherit the address size of the segment they are declared in.
947 The address size of a segment may be changed, by using an optional address
948 size modifier. See the <tt/<ref id=".SEGMENT" name="segment directive">/ for
949 an explanation on how this is done.
952 <sect1>Address sizes of symbols<p>
957 <sect1>Memory models<p>
959 The default address size of a segment depends on the memory model used. Since
960 labels inherit the address size from the segment they are declared in,
961 changing the memory model is an easy way to change the address size of many
967 <sect>Pseudo variables<label id="pseudo-variables"><p>
969 Pseudo variables are readable in all cases, and in some special cases also
974 Reading this pseudo variable will return the program counter at the start
975 of the current input line.
977 Assignment to this variable is possible when <tt/<ref id=".FEATURE"
978 name=".FEATURE pc_assignment">/ is used. Note: You should not use
979 assignments to <tt/*/, use <tt/<ref id=".ORG" name=".ORG">/ instead.
982 <sect1><tt>.CPU</tt><label id=".CPU"><p>
984 Reading this pseudo variable will give a constant integer value that
985 tells which CPU is currently enabled. It can also tell which instruction
986 set the CPU is able to translate. The value read from the pseudo variable
987 should be further examined by using one of the constants defined by the
988 "cpu" macro package (see <tt/<ref id=".MACPACK" name=".MACPACK">/).
990 It may be used to replace the .IFPxx pseudo instructions or to construct
991 even more complex expressions.
997 .if (.cpu .bitand CPU_ISET_65816)
1009 <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"><p>
1011 This builtin pseudo variable is only available in macros. It is replaced by
1012 the actual number of parameters that were given in the macro invocation.
1017 .macro foo arg1, arg2, arg3
1018 .if .paramcount <> 3
1019 .error "Too few parameters for macro foo"
1025 See section <ref id="macros" name="Macros">.
1028 <sect1><tt>.TIME</tt><label id=".TIME"><p>
1030 Reading this pseudo variable will give a constant integer value that
1031 represents the current time in POSIX standard (as seconds since the
1034 It may be used to encode the time of translation somewhere in the created
1040 .dword .time ; Place time here
1044 <sect1><tt>.VERSION</tt><label id=".VERSION"><p>
1046 Reading this pseudo variable will give the assembler version according to
1047 the following formula:
1049 VER_MAJOR*$100 + VER_MINOR*$10 + VER_PATCH
1051 It may be used to encode the assembler version or check the assembler for
1052 special features not available with older versions.
1056 Version 2.11.1 of the assembler will return $2B1 as numerical constant when
1057 reading the pseudo variable <tt/.VERSION/.
1061 <sect>Pseudo functions<label id="pseudo-functions"><p>
1063 Pseudo functions expect their arguments in parenthesis, and they have a result,
1064 either a string or an expression.
1067 <sect1><tt>.BANKBYTE</tt><label id=".BANKBYTE"><p>
1069 The function returns the bank byte (that is, bits 16-23) of its argument.
1070 It works identical to the '^' operator.
1072 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1073 <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>
1076 <sect1><tt>.BLANK</tt><label id=".BLANK"><p>
1078 Builtin function. The function evaluates its argument in braces and
1079 yields "false" if the argument is non blank (there is an argument), and
1080 "true" if there is no argument. As an example, the <tt/.IFBLANK/ statement
1088 <sect1><tt>.CONCAT</tt><label id=".CONCAT"><p>
1090 Builtin string function. The function allows to concatenate a list of string
1091 constants separated by commas. The result is a string constant that is the
1092 concatentation of all arguments. This function is most useful in macros and
1093 when used together with the <tt/.STRING/ builtin function. The function may
1094 be used in any case where a string constant is expected.
1099 .include .concat ("myheader", ".", "inc")
1102 This is the same as the command
1105 .include "myheader.inc"
1109 <sect1><tt>.CONST</tt><label id=".CONST"><p>
1111 Builtin function. The function evaluates its argument in braces and
1112 yields "true" if the argument is a constant expression (that is, an
1113 expression that yields a constant value at assembly time) and "false"
1114 otherwise. As an example, the .IFCONST statement may be replaced by
1121 <sect1><tt>.HIBYTE</tt><label id=".HIBYTE"><p>
1123 The function returns the high byte (that is, bits 8-15) of its argument.
1124 It works identical to the '>' operator.
1126 See: <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>,
1127 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1130 <sect1><tt>.HIWORD</tt><label id=".HIWORD"><p>
1132 The function returns the high word (that is, bits 16-31) of its argument.
1134 See: <tt><ref id=".LOWORD" name=".LOWORD"></tt>
1137 <sect1><tt>.LEFT</tt><label id=".LEFT"><p>
1139 Builtin function. Extracts the left part of a given token list.
1144 .LEFT (<int expr>, <token list>)
1147 The first integer expression gives the number of tokens to extract from
1148 the token list. The second argument is the token list itself.
1152 To check in a macro if the given argument has a '#' as first token
1153 (immidiate addressing mode), use something like this:
1158 .if (.match (.left (1, arg), #))
1160 ; ldax called with immidiate operand
1168 See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT"
1169 name=".RIGHT"></tt> builtin functions.
1172 <sect1><tt>.LOBYTE</tt><label id=".LOBYTE"><p>
1174 The function returns the low byte (that is, bits 0-7) of its argument.
1175 It works identical to the '<' operator.
1177 See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>,
1178 <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt>
1181 <sect1><tt>.LOWORD</tt><label id=".LOWORD"><p>
1183 The function returns the low word (that is, bits 0-15) of its argument.
1185 See: <tt><ref id=".HIWORD" name=".HIWORD"></tt>
1188 <sect1><tt>.MATCH</tt><label id=".MATCH"><p>
1190 Builtin function. Matches two token lists against each other. This is
1191 most useful within macros, since macros are not stored as strings, but
1197 .MATCH(<token list #1>, <token list #2>)
1200 Both token list may contain arbitrary tokens with the exception of the
1201 terminator token (comma resp. right parenthesis) and
1208 Often a macro parameter is used for any of the token lists.
1210 Please note that the function does only compare tokens, not token
1211 attributes. So any number is equal to any other number, regardless of the
1212 actual value. The same is true for strings. If you need to compare tokens
1213 <em/and/ token attributes, use the <tt><ref id=".XMATCH"
1214 name=".XMATCH"></tt> function.
1218 Assume the macro <tt/ASR/, that will shift right the accumulator by one,
1219 while honoring the sign bit. The builtin processor instructions will allow
1220 an optional "A" for accu addressing for instructions like <tt/ROL/ and
1221 <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function
1222 to check for this and print and error for invalid calls.
1227 .if (.not .blank(arg)) .and (.not .match (arg, a))
1228 .error "Syntax error"
1231 cmp #$80 ; Bit 7 into carry
1232 lsr a ; Shift carry into bit 7
1237 The macro will only accept no arguments, or one argument that must be the
1238 reserved keyword "A".
1240 See: <tt><ref id=".XMATCH" name=".XMATCH"></tt>
1243 <sect1><tt>.MID</tt><label id=".MID"><p>
1245 Builtin function. Takes a starting index, a count and a token list as
1246 arguments. Will return part of the token list.
1251 .MID (<int expr>, <int expr>, <token list>)
1254 The first integer expression gives the starting token in the list (the
1255 first token has index 0). The second integer expression gives the number
1256 of tokens to extract from the token list. The third argument is the
1261 To check in a macro if the given argument has a '<tt/#/' as first token
1262 (immidiate addressing mode), use something like this:
1267 .if (.match (.mid (0, 1, arg), #))
1269 ; ldax called with immidiate operand
1277 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT"
1278 name=".RIGHT"></tt> builtin functions.
1281 <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"><p>
1283 Builtin function. The function expects an identifier as argument in braces.
1284 The argument is evaluated, and the function yields "true" if the identifier
1285 is a symbol that has already been referenced somewhere in the source file up
1286 to the current position. Otherwise the function yields false. As an example,
1287 the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by
1293 See: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
1296 <sect1><tt>.RIGHT</tt><label id=".RIGHT"><p>
1298 Builtin function. Extracts the right part of a given token list.
1303 .RIGHT (<int expr>, <token list>)
1306 The first integer expression gives the number of tokens to extract from
1307 the token list. The second argument is the token list itself.
1309 See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID"
1310 name=".MID"></tt> builtin functions.
1313 <sect1><tt>.SIZEOF</tt><label id=".SIZEOF"><p>
1315 <tt/.SIZEOF/ is a pseudo function that returns the size of its argument. The
1316 argument can be a struct/union, a struct member, a procedure, or a label. In
1317 case of a procedure or label, its size is defined by the amount of data
1318 placed in the segment where the label is relative to. If a line of code
1319 switches segments (for example in a macro) data placed in other segments
1320 does not count for the size.
1322 Please note that a symbol or scope must exist, before it is used together with
1323 <tt/.SIZEOF/ (this may get relaxed later, but will always be true for scopes).
1324 A scope has preference over a symbol with the same name, so if the last part
1325 of a name represents both, a scope and a symbol, the scope is choosen over the
1328 After the following code:
1331 .struct Point ; Struct size = 4
1336 P: .tag Point ; Declare a point
1337 @P: .tag Point ; Declare another point
1349 .data ; Segment switch!!!
1355 <tag><tt/.sizeof(Point)/</tag>
1356 will have the value 4, because this is the size of struct <tt/Point/.
1358 <tag><tt/.sizeof(Point::xcoord)/</tag>
1359 will have the value 2, because this is the size of the member <tt/xcoord/
1360 in struct <tt/Point/.
1362 <tag><tt/.sizeof(P)/</tag>
1363 will have the value 4, this is the size of the data declared on the same
1364 source line as the label <tt/P/, which is in the same segment that <tt/P/
1367 <tag><tt/.sizeof(@P)/</tag>
1368 will have the value 4, see above. The example demonstrates that <tt/.SIZEOF/
1369 does also work for cheap local symbols.
1371 <tag><tt/.sizeof(Code)/</tag>
1372 will have the value 3, since this is amount of data emitted into the code
1373 segment, the segment that was active when <tt/Code/ was entered. Note that
1374 this value includes the amount of data emitted in child scopes (in this
1375 case <tt/Code::Inner/).
1377 <tag><tt/.sizeof(Code::Inner)/</tag>
1378 will have the value 1 as expected.
1380 <tag><tt/.sizeof(Data)/</tag>
1381 will have the value 0. Data is emitted within the scope <tt/Data/, but since
1382 the segment is switched after entry, this data is emitted into another
1387 <sect1><tt>.STRAT</tt><label id=".STRAT"><p>
1389 Builtin function. The function accepts a string and an index as
1390 arguments and returns the value of the character at the given position
1391 as an integer value. The index is zero based.
1397 ; Check if the argument string starts with '#'
1398 .if (.strat (Arg, 0) = '#')
1405 <sect1><tt>.STRING</tt><label id=".STRING"><p>
1407 Builtin function. The function accepts an argument in braces and converts
1408 this argument into a string constant. The argument may be an identifier, or
1409 a constant numeric value.
1411 Since you can use a string in the first place, the use of the function may
1412 not be obvious. However, it is useful in macros, or more complex setups.
1417 ; Emulate other assemblers:
1419 .segment .string(name)
1424 <sect1><tt>.STRLEN</tt><label id=".STRLEN"><p>
1426 Builtin function. The function accepts a string argument in braces and
1427 eveluates to the length of the string.
1431 The following macro encodes a string as a pascal style string with
1432 a leading length byte.
1436 .byte .strlen(Arg), Arg
1441 <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"><p>
1443 Builtin function. The function accepts a token list in braces. The
1444 function result is the number of tokens given as argument.
1448 The <tt/ldax/ macro accepts the '#' token to denote immidiate addressing (as
1449 with the normal 6502 instructions). To translate it into two separate 8 bit
1450 load instructions, the '#' token has to get stripped from the argument:
1454 .if (.match (.mid (0, 1, arg), #))
1455 ; ldax called with immidiate operand
1456 lda #<(.right (.tcount (arg)-1, arg))
1457 ldx #>(.right (.tcount (arg)-1, arg))
1465 <sect1><tt>.XMATCH</tt><label id=".XMATCH"><p>
1467 Builtin function. Matches two token lists against each other. This is
1468 most useful within macros, since macros are not stored as strings, but
1474 .XMATCH(<token list #1>, <token list #2>)
1477 Both token list may contain arbitrary tokens with the exception of the
1478 terminator token (comma resp. right parenthesis) and
1485 Often a macro parameter is used for any of the token lists.
1487 The function compares tokens <em/and/ token values. If you need a function
1488 that just compares the type of tokens, have a look at the <tt><ref
1489 id=".MATCH" name=".MATCH"></tt> function.
1491 See: <tt><ref id=".MATCH" name=".MATCH"></tt>
1495 <sect>Control commands<label id="control-commands"><p>
1497 Here's a list of all control commands and a description, what they do:
1500 <sect1><tt>.A16</tt><label id=".A16"><p>
1502 Valid only in 65816 mode. Switch the accumulator to 16 bit.
1504 Note: This command will not emit any code, it will tell the assembler to
1505 create 16 bit operands for immediate accumulator adressing mode.
1507 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1510 <sect1><tt>.A8</tt><label id=".A8"><p>
1512 Valid only in 65816 mode. Switch the accumulator to 8 bit.
1514 Note: This command will not emit any code, it will tell the assembler to
1515 create 8 bit operands for immediate accu adressing mode.
1517 See also: <tt><ref id=".SMART" name=".SMART"></tt>
1520 <sect1><tt>.ADDR</tt><label id=".ADDR"><p>
1522 Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and
1523 may be used for better readability if the data words are address values. In
1524 65816 mode, the address is forced to be 16 bit wide to fit into the current
1525 segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command
1526 must be followed by a sequence of (not necessarily constant) expressions.
1531 .addr $0D00, $AF13, _Clear
1534 See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD"
1538 <sect1><tt>.ALIGN</tt><label id=".ALIGN"><p>
1540 Align data to a given boundary. The command expects a constant integer
1541 argument that must be a power of two, plus an optional second argument
1542 in byte range. If there is a second argument, it is used as fill value,
1543 otherwise the value defined in the linker configuration file is used
1544 (the default for this value is zero).
1546 Since alignment depends on the base address of the module, you must
1547 give the same (or a greater) alignment for the segment when linking.
1548 The linker will give you a warning, if you don't do that.
1557 <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"><p>
1559 Define a string with a trailing zero.
1564 Msg: .asciiz "Hello world"
1567 This will put the string "Hello world" followed by a binary zero into
1568 the current segment. There may be more strings separated by commas, but
1569 the binary zero is only appended once (after the last one).
1572 <sect1><tt>.ASSERT</tt><label id=".ASSERT"><p>
1574 Add an assertion. The command is followed by an expression, an action
1575 specifier and a message that is output in case the assertion fails. The
1576 action specifier may be one of <tt/warning/ or <tt/error/. The assertion
1577 is passed to the linker and will be evaluated when segment placement has
1583 .assert * = $8000, error, "Code not at $8000"
1586 The example assertion will check that the current location is at $8000,
1587 when the output file is written, and abort with an error if this is not
1588 the case. More complex expressions are possible. The action specifier
1589 <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs
1590 an error message. In the latter case, generation if the output file is
1594 <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"><p>
1596 Is followed by a plus or a minus character. When switched on (using a
1597 +), undefined symbols are automatically marked as import instead of
1598 giving errors. When switched off (which is the default so this does not
1599 make much sense), this does not happen and an error message is
1600 displayed. The state of the autoimport flag is evaluated when the
1601 complete source was translated, before outputing actual code, so it is
1602 <em/not/ possible to switch this feature on or off for separate sections
1603 of code. The last setting is used for all symbols.
1605 You should probably not use this switch because it delays error
1606 messages about undefined symbols until the link stage. The cc65
1607 compiler (which is supposed to produce correct assembler code in all
1608 circumstances, something which is not true for most assembler
1609 programmers) will insert this command to avoid importing each and every
1610 routine from the runtime library.
1615 .autoimport + ; Switch on auto import
1619 <sect1><tt>.BSS</tt><label id=".BSS"><p>
1621 Switch to the BSS segment. The name of the BSS segment is always "BSS",
1622 so this is a shortcut for
1628 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1631 <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"><p>
1633 Define byte sized data. Must be followed by a sequence of (byte ranged)
1634 expressions or strings.
1640 .byt "world", $0D, $00
1644 <sect1><tt>.CASE</tt><label id=".CASE"><p>
1646 Switch on or off case sensitivity on identifiers. The default is off
1647 (that is, identifiers are case sensitive), but may be changed by the
1648 -i switch on the command line.
1649 The command must be followed by a '+' or '-' character to switch the
1650 option on or off respectively.
1655 .case - ; Identifiers are not case sensitive
1659 <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"><p>
1661 Apply a custom mapping for characters. The command is followed by two
1662 numbers in the range 1..255. The first one is the index of the source
1663 character, the second one is the mapping. The mapping applies to all
1664 character and string constants when they generate output, and overrides
1665 a mapping table specified with the <tt><ref id="option-t" name="-t"></tt>
1666 command line switch.
1671 .charmap $41, $61 ; Map 'A' to 'a'
1675 <sect1><tt>.CODE</tt><label id=".CODE"><p>
1677 Switch to the CODE segment. The name of the CODE segment is always
1678 "CODE", so this is a shortcut for
1684 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1687 <sect1><tt>.CONDES</tt><label id=".CONDES"><p>
1689 Export a symbol and mark it in a special way. The linker is able to build
1690 tables of all such symbols. This may be used to automatically create a list
1691 of functions needed to initialize linked library modules.
1693 Note: The linker has a feature to build a table of marked routines, but it
1694 is your code that must call these routines, so just declaring a symbol with
1695 <tt/.CONDES/ does nothing by itself.
1697 All symbols are exported as an absolute (16 bit) symbol. You don't need to
1698 use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this
1699 is implied by <tt/.CONDES/.
1701 <tt/.CONDES/ is followed by the type, which may be <tt/constructor/,
1702 <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as
1703 specifiying <tt/constructor/ and 1 is equal to specifying <tt/destructor/).
1704 The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
1705 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands are actually shortcuts
1706 for <tt/.CONDES/ with a type of <tt/constructor/ resp. <tt/destructor/.
1708 After the type, an optional priority may be specified. Higher numeric values
1709 mean higher priority. If no priority is given, the default priority of 7 is
1710 used. Be careful when assigning priorities to your own module constructors
1711 so they won't interfere with the ones in the cc65 library.
1716 .condes ModuleInit, constructor
1717 .condes ModInit, 0, 16
1720 See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
1721 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
1722 <ref id="condes" name="Module constructors/destructors"> explaining the
1723 feature in more detail.
1726 <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"><p>
1728 Export a symbol and mark it as a module constructor. This may be used
1729 together with the linker to build a table of constructor subroutines that
1730 are called by the startup code.
1732 Note: The linker has a feature to build a table of marked routines, but it
1733 is your code that must call these routines, so just declaring a symbol as
1734 constructor does nothing by itself.
1736 A constructor is always exported as an absolute (16 bit) symbol. You don't
1737 need to use an additional <tt/.export/ statement, this is implied by
1738 <tt/.constructor/. It may have an optional priority that is separated by a
1739 comma. Higher numeric values mean a higher priority. If no priority is
1740 given, the default priority of 7 is used. Be careful when assigning
1741 priorities to your own module constructors so they won't interfere with the
1742 ones in the cc65 library.
1747 .constructor ModuleInit
1748 .constructor ModInit, 16
1751 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1752 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section
1753 <ref id="condes" name="Module constructors/destructors"> explaining the
1754 feature in more detail.
1757 <sect1><tt>.DATA</tt><label id=".DATA"><p>
1759 Switch to the DATA segment. The name of the DATA segment is always
1760 "DATA", so this is a shortcut for
1766 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
1769 <sect1><tt>.DBYT</tt><label id=".DBYT"><p>
1771 Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to
1772 create word sized data in native 65XX format). Must be followed by a
1773 sequence of (word ranged) expressions.
1781 This will emit the bytes
1787 into the current segment in that order.
1790 <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"><p>
1792 Switch on or off debug info generation. The default is off (that is,
1793 the object file will not contain debug infos), but may be changed by the
1794 -g switch on the command line.
1795 The command must be followed by a '+' or '-' character to switch the
1796 option on or off respectively.
1801 .debuginfo + ; Generate debug info
1805 <sect1><tt>.DEFINE</tt><label id=".DEFINE"><p>
1807 Start a define style macro definition. The command is followed by an
1808 identifier (the macro name) and optionally by a list of formal arguments
1810 See section <ref id="macros" name="Macros">.
1813 <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"><p>
1815 Builtin function. The function expects an identifier as argument in braces.
1816 The argument is evaluated, and the function yields "true" if the identifier
1817 is a symbol that is already defined somewhere in the source file up to the
1818 current position. Otherwise the function yields false. As an example, the
1819 <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by
1826 <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"><p>
1828 Export a symbol and mark it as a module destructor. This may be used
1829 together with the linker to build a table of destructor subroutines that
1830 are called by the startup code.
1832 Note: The linker has a feature to build a table of marked routines, but it
1833 is your code that must call these routines, so just declaring a symbol as
1834 constructor does nothing by itself.
1836 A destructor is always exported as an absolute (16 bit) symbol. You don't
1837 need to use an additional <tt/.export/ statement, this is implied by
1838 <tt/.destructor/. It may have an optional priority that is separated by a
1839 comma. Higher numerical values mean a higher priority. If no priority is
1840 given, the default priority of 7 is used. Be careful when assigning
1841 priorities to your own module destructors so they won't interfere with the
1842 ones in the cc65 library.
1847 .destructor ModuleDone
1848 .destructor ModDone, 16
1851 See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref
1852 id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate
1853 section <ref id="condes" name="Module constructors/destructors"> explaining
1854 the feature in more detail.
1857 <sect1><tt>.DWORD</tt><label id=".DWORD"><p>
1859 Define dword sized data (4 bytes) Must be followed by a sequence of
1865 .dword $12344512, $12FA489
1869 <sect1><tt>.ELSE</tt><label id=".ELSE"><p>
1871 Conditional assembly: Reverse the current condition.
1874 <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"><p>
1876 Conditional assembly: Reverse current condition and test a new one.
1879 <sect1><tt>.END</tt><label id=".END"><p>
1881 Forced end of assembly. Assembly stops at this point, even if the command
1882 is read from an include file.
1885 <sect1><tt>.ENDENUM</tt><label id=".ENDENUM"><p>
1887 End a <tt><ref id=".ENUM" name=".ENUM"></tt> declaration.
1890 <sect1><tt>.ENDIF</tt><label id=".ENDIF"><p>
1892 Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or
1893 <tt><ref id=".ELSE" name=".ELSE"></tt> branch.
1896 <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"><p>
1898 End of macro definition (see section <ref id="macros" name="Macros">).
1901 <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"><p>
1903 End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>).
1906 <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"><p>
1908 End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block.
1911 <sect1><tt>.ENDSCOPE</tt><label id=".ENDSCOPE"><p>
1913 End of local lexical level (see <tt/<ref id=".SCOPE" name=".SCOPE">/).
1916 <sect1><tt>.ENDSTRUCT</tt><label id=".ENDSTRUCT"><p>
1918 Ends a struct definition. See the <tt/<ref id=".STRUCT" name=".STRUCT">/
1919 command and the separate section named <ref id="structs" name=""Structs
1923 <sect1><tt>.ENUM</tt><label id=".ENUM"><p>
1925 Start an enumeration. This directive is very similar to the C <tt/enum/
1926 keyword. If a name is given, a new scope is created for the enumeration,
1927 otherwise the enumeration members are placed in the enclosing scope.
1929 In the enumeration body, symbols are declared. The first symbol has a value
1930 of zero, and each following symbol will get the value of the preceeding plus
1931 one. This behaviour may be overriden by an explicit assignment. Two symbols
1932 may have the same value.
1944 Above example will create a new scope named <tt/errorcodes/ with three
1945 symbols in it that get the values 0, 1 and 2 respectively. Another way
1946 to write this would have been:
1956 Please note that explicit scoping must be used to access the identifiers:
1959 .word errorcodes::no_error
1962 A more complex example:
1971 EWOULDBLOCK = EAGAIN
1975 In this example, the enumeration does not have a name, which means that the
1976 members will be visible in the enclosing scope and can be used in this scope
1977 without explicit scoping. The first member (<tt/EUNKNOWN/) has the value -1.
1978 The value for the following members is incremented by one, so <tt/EOK/ would
1979 be zero and so on. <tt/EWOULDBLOCK/ is an alias for <tt/EGAIN/, so it has an
1980 override for the value using an already defined symbol.
1983 <sect1><tt>.ERROR</tt><label id=".ERROR"><p>
1985 Force an assembly error. The assembler will output an error message
1986 preceeded by "User error" and will <em/not/ produce an object file.
1988 This command may be used to check for initial conditions that must be
1989 set before assembling a source file.
1999 .error "Must define foo or bar!"
2003 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
2004 id=".OUT" name=".OUT"></tt> directives.
2007 <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"><p>
2009 Abort a macro expansion immidiately. This command is often useful in
2010 recursive macros. See separate section <ref id="macros" name="Macros">.
2013 <sect1><tt>.EXPORT</tt><label id=".EXPORT"><p>
2015 Make symbols accessible from other modules. Must be followed by a comma
2016 separated list of symbols to export, with each one optionally followed by
2017 an address specification. The default is to export the symbol with the
2018 address size it actually has. The assembler will issue a warning, if the
2019 symbol is exported with an address size smaller than the actual address
2029 See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt>
2032 <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"><p>
2034 Make symbols accessible from other modules. Must be followed by a comma
2035 separated list of symbols to export. The exported symbols are explicitly
2036 marked as zero page symols.
2044 See: <tt><ref id=".EXPORT" name=".EXPORT"></tt>
2047 <sect1><tt>.FARADDR</tt><label id=".FARADDR"><p>
2049 Define far (24 bit) address data. The command must be followed by a
2050 sequence of (not necessarily constant) expressions.
2055 .faraddr DrawCircle, DrawRectangle, DrawHexagon
2058 See: <tt><ref id=".ADDR" name=".ADDR"></tt>
2061 <sect1><tt>.FEATURE</tt><label id=".FEATURE"><p>
2063 This directive may be used to enable one or more compatibility features
2064 of the assembler. While the use of <tt/.FEATURE/ should be avoided when
2065 possible, it may be useful when porting sources written for other
2066 assemblers. There is no way to switch a feature off, once you have
2067 enabled it, so using
2073 will enable the feature until end of assembly is reached.
2075 The following features are available:
2079 <tag><tt>at_in_identifiers</tt></tag>
2081 Accept the at character (`@') as a valid character in identifiers. The
2082 at character is not allowed to start an identifier, even with this
2085 <tag><tt>dollar_in_identifiers</tt></tag>
2087 Accept the dollar sign (`$') as a valid character in identifiers. The
2088 at character is not allowed to start an identifier, even with this
2091 <tag><tt>dollar_is_pc</tt></tag>
2093 The dollar sign may be used as an alias for the star (`*'), which
2094 gives the value of the current PC in expressions.
2095 Note: Assignment to the pseudo variable is not allowed.
2097 <tag><tt>labels_without_colons</tt></tag>
2099 Allow labels without a trailing colon. These labels are only accepted,
2100 if they start at the beginning of a line (no leading white space).
2102 <tag><tt>leading_dot_in_identifiers</tt></tag>
2104 Accept the dot (`.') as the first character of an identifier. This may be
2105 used for example to create macro names that start with a dot emulating
2106 control directives of other assemblers. Note however, that none of the
2107 reserved keywords built into the assembler, that starts with a dot, may be
2108 overridden. When using this feature, you may also get into trouble if
2109 later versions of the assembler define new keywords starting with a dot.
2111 <tag><tt>loose_char_term</tt></tag>
2113 Accept single quotes as well as double quotes as terminators for char
2116 <tag><tt>loose_string_term</tt></tag>
2118 Accept single quotes as well as double quotes as terminators for string
2121 <tag><tt>missing_char_term</tt></tag>
2123 Accept single quoted character constants where the terminating quote is
2128 <bf/Note:/ This does not work in conjunction with <tt/.FEATURE
2129 loose_string_term/, since in this case the input would be ambigous.
2131 <tag><tt>pc_assignment</tt></tag>
2133 Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/
2134 is enabled). Such an assignment is handled identical to the <tt><ref
2135 id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
2136 removing the lines with the assignments may also be an option when porting
2137 code written for older assemblers).
2139 <tag><tt>ubiquitous_idents</tt></tag>
2141 Allow the use of instructions names as names for macros and symbols. This
2142 makes it possible to "overload" instructions by defining a macro with the
2143 same name. This does also make it possible to introduce hard to find errors
2144 in your code, so be careful!
2148 It is also possible to specify features on the command line using the
2149 <tt><ref id="option--feature" name="--feature"></tt> command line option.
2150 This is useful when translating sources written for older assemblers, when
2151 you don't want to change the source code.
2153 As an example, to translate sources written for Andre Fachats xa65
2154 assembler, the features
2157 labels_without_colons, pc_assignment, loose_char_term
2160 may be helpful. They do not make ca65 completely compatible, so you may not
2161 be able to translate the sources without changes, even when enabling these
2162 features. However, I have found several sources that translate without
2163 problems when enabling these features on the command line.
2166 <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"><p>
2168 Insert an option string into the object file. There are two forms of
2169 this command, one specifies the option by a keyword, the second
2170 specifies it as a number. Since usage of the second one needs knowledge
2171 of the internal encoding, its use is not recommended and I will only
2172 describe the first form here.
2174 The command is followed by one of the keywords
2182 a comma and a string. The option is written into the object file
2183 together with the string value. This is currently unidirectional and
2184 there is no way to actually use these options once they are in the
2190 .fileopt comment, "Code stolen from my brother"
2191 .fileopt compiler, "BASIC 2.0"
2192 .fopt author, "J. R. User"
2196 <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"><p>
2198 Import an absolute symbol from another module. The command is followed by a
2199 comma separated list of symbols to import. The command is similar to <tt>
2200 <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always
2201 written to the generated object file, even if the symbol is never referenced
2202 (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import
2203 references for unused symbols).
2208 .forceimport needthisone, needthistoo
2211 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2214 <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"><p>
2216 Declare symbols as global. Must be followed by a comma separated list of
2217 symbols to declare. Symbols from the list, that are defined somewhere in the
2218 source, are exported, all others are imported. Additional <tt><ref
2219 id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT"
2220 name=".EXPORT"></tt> commands for the same symbol are allowed.
2229 <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"><p>
2231 Declare symbols as global. Must be followed by a comma separated list of
2232 symbols to declare. Symbols from the list, that are defined somewhere in the
2233 source, are exported, all others are imported. Additional <tt><ref
2234 id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP"
2235 name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols
2236 in the list are explicitly marked as zero page symols.
2245 <sect1><tt>.I16</tt><label id=".I16"><p>
2247 Valid only in 65816 mode. Switch the index registers to 16 bit.
2249 Note: This command will not emit any code, it will tell the assembler to
2250 create 16 bit operands for immediate operands.
2252 See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART"
2253 name=".SMART"></tt> commands.
2256 <sect1><tt>.I8</tt><label id=".I8"><p>
2258 Valid only in 65816 mode. Switch the index registers to 8 bit.
2260 Note: This command will not emit any code, it will tell the assembler to
2261 create 8 bit operands for immediate operands.
2263 See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART"
2264 name=".SMART"></tt> commands.
2267 <sect1><tt>.IF</tt><label id=".IF"><p>
2269 Conditional assembly: Evalute an expression and switch assembler output
2270 on or off depending on the expression. The expression must be a constant
2271 expression, that is, all operands must be defined.
2273 A expression value of zero evaluates to FALSE, any other value evaluates
2277 <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"><p>
2279 Conditional assembly: Check if there are any remaining tokens in this line,
2280 and evaluate to FALSE if this is the case, and to TRUE otherwise. If the
2281 condition is not true, further lines are not assembled until an <tt><ref
2282 id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2283 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2285 This command is often used to check if a macro parameter was given. Since an
2286 empty macro parameter will evaluate to nothing, the condition will evaluate
2287 to FALSE if an empty parameter was given.
2301 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2304 <sect1><tt>.IFCONST</tt><label id=".IFCONST"><p>
2306 Conditional assembly: Evaluate an expression and switch assembler output
2307 on or off depending on the constness of the expression.
2309 A const expression evaluates to to TRUE, a non const expression (one
2310 containing an imported or currently undefined symbol) evaluates to
2313 See also: <tt><ref id=".CONST" name=".CONST"></tt>
2316 <sect1><tt>.IFDEF</tt><label id=".IFDEF"><p>
2318 Conditional assembly: Check if a symbol is defined. Must be followed by
2319 a symbol name. The condition is true if the the given symbol is already
2320 defined, and false otherwise.
2322 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2325 <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"><p>
2327 Conditional assembly: Check if there are any remaining tokens in this line,
2328 and evaluate to TRUE if this is the case, and to FALSE otherwise. If the
2329 condition is not true, further lines are not assembled until an <tt><ref
2330 id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or
2331 <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive.
2333 This command is often used to check if a macro parameter was given.
2334 Since an empty macro parameter will evaluate to nothing, the condition
2335 will evaluate to FALSE if an empty parameter was given.
2348 See also: <tt><ref id=".BLANK" name=".BLANK"></tt>
2351 <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"><p>
2353 Conditional assembly: Check if a symbol is defined. Must be followed by
2354 a symbol name. The condition is true if the the given symbol is not
2355 defined, and false otherwise.
2357 See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt>
2360 <sect1><tt>.IFNREF</tt><label id=".IFNREF"><p>
2362 Conditional assembly: Check if a symbol is referenced. Must be followed
2363 by a symbol name. The condition is true if if the the given symbol was
2364 not referenced before, and false otherwise.
2366 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2369 <sect1><tt>.IFP02</tt><label id=".IFP02"><p>
2371 Conditional assembly: Check if the assembler is currently in 6502 mode
2372 (see <tt><ref id=".P02" name=".P02"></tt> command).
2375 <sect1><tt>.IFP816</tt><label id=".IFP816"><p>
2377 Conditional assembly: Check if the assembler is currently in 65816 mode
2378 (see <tt><ref id=".P816" name=".P816"></tt> command).
2381 <sect1><tt>.IFPC02</tt><label id=".IFPC02"><p>
2383 Conditional assembly: Check if the assembler is currently in 65C02 mode
2384 (see <tt><ref id=".PC02" name=".PC02"></tt> command).
2387 <sect1><tt>.IFPSC02</tt><label id=".IFPSC02"><p>
2389 Conditional assembly: Check if the assembler is currently in 65SC02 mode
2390 (see <tt><ref id=".PSC02" name=".PSC02"></tt> command).
2393 <sect1><tt>.IFREF</tt><label id=".IFREF"><p>
2395 Conditional assembly: Check if a symbol is referenced. Must be followed
2396 by a symbol name. The condition is true if if the the given symbol was
2397 referenced before, and false otherwise.
2399 This command may be used to build subroutine libraries in include files
2400 (you may use separate object modules for this purpose too).
2405 .ifref ToHex ; If someone used this subroutine
2406 ToHex: tay ; Define subroutine
2412 See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt>
2415 <sect1><tt>.IMPORT</tt><label id=".IMPORT"><p>
2417 Import a symbol from another module. The command is followed by a comma
2418 separated list of symbols to import, with each one optionally followed by
2419 an address specification.
2425 .import bar: zeropage
2428 See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt>
2431 <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"><p>
2433 Import a symbol from another module. The command is followed by a comma
2434 separated list of symbols to import. The symbols are explicitly imported
2435 as zero page symbols (that is, symbols with values in byte range).
2443 See: <tt><ref id=".IMPORT" name=".IMPORT"></tt>
2446 <sect1><tt>.INCBIN</tt><label id=".INCBIN"><p>
2448 Include a file as binary data. The command expects a string argument
2449 that is the name of a file to include literally in the current segment.
2450 In addition to that, a start offset and a size value may be specified,
2451 separated by commas. If no size is specified, all of the file from the
2452 start offset to end-of-file is used. If no start position is specified
2453 either, zero is assume (which means that the whole file is inserted).
2458 ; Include whole file
2459 .incbin "sprites.dat"
2461 ; Include file starting at offset 256
2462 .incbin "music.dat", $100
2464 ; Read 100 bytes starting at offset 200
2465 .incbin "graphics.dat", 200, 100
2469 <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"><p>
2471 Include another file. Include files may be nested up to a depth of 16.
2480 <sect1><tt>.LINECONT</tt><label id=".LINECONT"><p>
2482 Switch on or off line continuations using the backslash character
2483 before a newline. The option is off by default.
2484 Note: Line continuations do not work in a comment. A backslash at the
2485 end of a comment is treated as part of the comment and does not trigger
2487 The command must be followed by a '+' or '-' character to switch the
2488 option on or off respectively.
2493 .linecont + ; Allow line continuations
2496 #$20 ; This is legal now
2500 <sect1><tt>.LIST</tt><label id=".LIST"><p>
2502 Enable output to the listing. The command must be followed by a boolean
2503 switch ("on", "off", "+" or "-") and will enable or disable listing
2505 The option has no effect if the listing is not enabled by the command line
2506 switch -l. If -l is used, an internal counter is set to 1. Lines are output
2507 to the listing file, if the counter is greater than zero, and suppressed if
2508 the counter is zero. Each use of <tt/.LIST/ will increment or decrement the
2514 .list on ; Enable listing output
2518 <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"><p>
2520 Set, how many bytes are shown in the listing for one source line. The
2521 default is 12, so the listing will show only the first 12 bytes for any
2522 source line that generates more than 12 bytes of code or data.
2523 The directive needs an argument, which is either "unlimited", or an
2524 integer constant in the range 4..255.
2529 .listbytes unlimited ; List all bytes
2530 .listbytes 12 ; List the first 12 bytes
2531 .incbin "data.bin" ; Include large binary file
2535 <sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
2537 This command may only be used inside a macro definition. It declares a
2538 list of identifiers as local to the macro expansion.
2540 A problem when using macros are labels: Since they don't change their name,
2541 you get a "duplicate symbol" error if the macro is expanded the second time.
2542 Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
2543 name mapped to an internal unique name (<tt/___ABCD__/) with each macro
2546 Some other assemblers start a new lexical block inside a macro expansion.
2547 This has some drawbacks however, since that will not allow <em/any/ symbol
2548 to be visible outside a macro, a feature that is sometimes useful. The
2549 <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
2550 to address the problem.
2552 You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
2556 <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"><p>
2558 Defines the character that start "cheap" local labels. You may use one
2559 of '@' and '?' as start character. The default is '@'.
2561 Cheap local labels are labels that are visible only between two non
2562 cheap labels. This way you can reuse identifiers like "<tt/loop/" without
2563 using explicit lexical nesting.
2570 Clear: lda #$00 ; Global label
2571 ?Loop: sta Mem,y ; Local label
2575 Sub: ... ; New global label
2576 bne ?Loop ; ERROR: Unknown identifier!
2580 <sect1><tt>.MACPACK</tt><label id=".MACPACK"><p>
2582 Insert a predefined macro package. The command is followed by an
2583 identifier specifying the macro package to insert. Available macro
2587 generic Defines generic macros like add and sub.
2588 longbranch Defines conditional long jump macros.
2589 cbm Defines the scrcode macro
2590 cpu Defines constants for the .CPU variable
2593 Including a macro package twice, or including a macro package that
2594 redefines already existing macros will lead to an error.
2599 .macpack longbranch ; Include macro package
2601 cmp #$20 ; Set condition codes
2602 jne Label ; Jump long on condition
2605 Macro packages are explained in more detail in section <ref
2606 id="macropackages" name="Macro packages">.
2609 <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"><p>
2611 Start a classic macro definition. The command is followed by an identifier
2612 (the macro name) and optionally by a comma separated list of identifiers
2613 that are macro parameters.
2615 See section <ref id="macros" name="Macros">.
2618 <sect1><tt>.ORG</tt><label id=".ORG"><p>
2620 Start a section of absolute code. The command is followed by a constant
2621 expression that gives the new PC counter location for which the code is
2622 assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to
2625 Please note that you <em/do not need/ this command in most cases. Placing
2626 code at a specific address is the job of the linker, not the assembler, so
2627 there is usually no reason to assemble code to a specific address.
2629 You may not switch segments while inside a section of absolute code.
2634 .org $7FF ; Emit code starting at $7FF
2638 <sect1><tt>.OUT</tt><label id=".OUT"><p>
2640 Output a string to the console without producing an error. This command
2641 is similiar to <tt/.ERROR/, however, it does not force an assembler error
2642 that prevents the creation of an object file.
2647 .out "This code was written by the codebuster(tm)"
2650 See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref
2651 id=".ERROR" name=".ERROR"></tt> directives.
2654 <sect1><tt>.P02</tt><label id=".P02"><p>
2656 Enable the 6502 instruction set, disable 65SC02, 65C02 and 65816
2657 instructions. This is the default if not overridden by the
2658 <tt><ref id="option--cpu" name="--cpu"></tt> command line option.
2660 See: <tt><ref id=".PC02" name=".PC02"></tt>, <tt><ref id=".PSC02"
2661 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2664 <sect1><tt>.P816</tt><label id=".P816"><p>
2666 Enable the 65816 instruction set. This is a superset of the 65SC02 and
2667 6502 instruction sets.
2669 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
2670 name=".PSC02"></tt> and <tt><ref id=".PC02" name=".PC02"></tt>
2673 <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"><p>
2675 Set the page length for the listing. Must be followed by an integer
2676 constant. The value may be "unlimited", or in the range 32 to 127. The
2677 statement has no effect if no listing is generated. The default value is -1
2678 (unlimited) but may be overridden by the <tt/--pagelength/ command line
2679 option. Beware: Since ca65 is a one pass assembler, the listing is generated
2680 after assembly is complete, you cannot use multiple line lengths with one
2681 source. Instead, the value set with the last <tt/.PAGELENGTH/ is used.
2686 .pagelength 66 ; Use 66 lines per listing page
2688 .pagelength unlimited ; Unlimited page length
2692 <sect1><tt>.PC02</tt><label id=".PC02"><p>
2694 Enable the 65C02 instructions set. This instruction set includes all
2695 6502 and 65SC02 instructions.
2697 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
2698 name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2701 <sect1><tt>.POPSEG</tt><label id=".POPSEG"><p>
2703 Pop the last pushed segment from the stack, and set it.
2705 This command will switch back to the segment that was last pushed onto the
2706 segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
2707 command, and remove this entry from the stack.
2709 The assembler will print an error message if the segment stack is empty
2710 when this command is issued.
2712 See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt>
2715 <sect1><tt>.PROC</tt><label id=".PROC"><p>
2717 Start a nested lexical level with the given name and adds a symbol with this
2718 name to the enclosing scope. All new symbols from now on are in the local
2719 lexical level and are accessible from outside only via <ref id="scopesyntax"
2720 name="explicit scope specification">. Symbols defined outside this local
2721 level may be accessed as long as their names are not used for new symbols
2722 inside the level. Symbols names in other lexical levels do not clash, so you
2723 may use the same names for identifiers. The lexical level ends when the
2724 <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read. Lexical levels
2725 may be nested up to a depth of 16 (this is an artificial limit to protect
2726 against errors in the source).
2728 Note: Macro names are always in the global level and in a separate name
2729 space. There is no special reason for this, it's just that I've never
2730 had any need for local macro definitions.
2735 .proc Clear ; Define Clear subroutine, start new level
2737 L1: sta Mem,y ; L1 is local and does not cause a
2738 ; duplicate symbol error if used in other
2741 bne L1 ; Reference local symbol
2743 .endproc ; Leave lexical level
2746 See: <tt/<ref id=".ENDPROC" name=".ENDPROC">/ and <tt/<ref id=".SCOPE"
2750 <sect1><tt>.PSC02</tt><label id=".PSC02"><p>
2752 Enable the 65SC02 instructions set. This instruction set includes all
2755 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PC02"
2756 name=".PC02"></tt> and <tt><ref id=".P816" name=".P816"></tt>
2759 <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"><p>
2761 Push the currently active segment onto a stack. The entries on the stack
2762 include the name of the segment and the segment type. The stack has a size
2765 <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt>
2766 to switch to another segment and to restore the old segment later, without
2767 even knowing the name and type of the current segment.
2769 The assembler will print an error message if the segment stack is already
2770 full, when this command is issued.
2772 See: <tt><ref id=".POPSEG" name=".POPSEG"></tt>
2775 <sect1><tt>.REPEAT</tt><label id=".REPEAT"><p>
2777 Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT"
2778 name=".ENDREPEAT"></tt> constant number of times. The command is followed by
2779 a constant expression that tells how many times the commands in the body
2780 should get repeated. Optionally, a comma and an identifier may be specified.
2781 If this identifier is found in the body of the repeat statement, it is
2782 replaced by the current repeat count (starting with zero for the first time
2783 the body is repeated).
2785 <tt/.REPEAT/ statements may be nested. If you use the same repeat count
2786 identifier for a nested <tt/.REPEAT/ statement, the one from the inner
2787 level will be used, not the one from the outer level.
2791 The following macro will emit a string that is "encrypted" in that all
2792 characters of the string are XORed by the value $55.
2796 .repeat .strlen(Arg), I
2797 .byte .strat(Arg, I) .xor $55
2802 See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt>
2805 <sect1><tt>.RELOC</tt><label id=".RELOC"><p>
2807 Switch back to relocatable mode. See the <tt><ref id=".ORG"
2808 name=".ORG"></tt> command.
2811 <sect1><tt>.RES</tt><label id=".RES"><p>
2813 Reserve storage. The command is followed by one or two constant
2814 expressions. The first one is mandatory and defines, how many bytes of
2815 storage should be defined. The second, optional expression must by a
2816 constant byte value that will be used as value of the data. If there
2817 is no fill value given, the linker will use the value defined in the
2818 linker configuration file (default: zero).
2823 ; Reserve 12 bytes of memory with value $AA
2828 <sect1><tt>.RODATA</tt><label id=".RODATA"><p>
2830 Switch to the RODATA segment. The name of the RODATA segment is always
2831 "RODATA", so this is a shortcut for
2837 The RODATA segment is a segment that is used by the compiler for
2838 readonly data like string constants.
2840 See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command.
2843 <sect1><tt>.SCOPE</tt><label id=".SCOPE"><p>
2845 Start a nested lexical level with the given name. All new symbols from now
2846 on are in the local lexical level and are accessible from outside only via
2847 <ref id="scopesyntax" name="explicit scope specification">. Symbols defined
2848 outside this local level may be accessed as long as their names are not used
2849 for new symbols inside the level. Symbols names in other lexical levels do
2850 not clash, so you may use the same names for identifiers. The lexical level
2851 ends when the <tt><ref id=".ENDSCOPE" name=".ENDSCOPE"></tt> command is
2852 read. Lexical levels may be nested up to a depth of 16 (this is an
2853 artificial limit to protect against errors in the source).
2855 Note: Macro names are always in the global level and in a separate name
2856 space. There is no special reason for this, it's just that I've never
2857 had any need for local macro definitions.
2862 .scope Error ; Start new scope named Error
2864 File = 1 ; File error
2865 Parse = 2 ; Parse error
2866 .endproc ; Close lexical level
2869 lda #Error::File ; Use symbol from scope Error
2872 See: <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/ and <tt/<ref id=".PROC"
2876 <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"><p>
2878 Switch to another segment. Code and data is always emitted into a
2879 segment, that is, a named section of data. The default segment is
2880 "CODE". There may be up to 254 different segments per object file
2881 (and up to 65534 per executable). There are shortcut commands for
2882 the most common segments ("CODE", "DATA" and "BSS").
2884 The command is followed by a string containing the segment name (there are
2885 some constraints for the name - as a rule of thumb use only those segment
2886 names that would also be valid identifiers). There may also be an optional
2887 address size separated by a colon. See the section covering <tt/<ref
2888 id="address-sizes" name="address sizes">/ for more information.
2890 The default address size for a segment depends on the memory model specified
2891 on the command line. The default is "absolute", which means that you don't
2892 have to use an address size modifier in most cases.
2894 "absolute" means that the is a segment with 16 bit (absolute) addressing.
2895 That is, the segment will reside somewhere in core memory outside the zero
2896 page. "zeropage" (8 bit) means that the segment will be placed in the zero
2897 page and direct (short) addressing is possible for data in this segment.
2899 Beware: Only labels in a segment with the zeropage attribute are marked
2900 as reachable by short addressing. The `*' (PC counter) operator will
2901 work as in other segments and will create absolute variable values.
2903 Please note that a segment cannot have two different address sizes. A
2904 segment specified as zeropage cannot be declared as being absolute later.
2909 .segment "ROM2" ; Switch to ROM2 segment
2910 .segment "ZP2": zeropage ; New direct segment
2911 .segment "ZP2" ; Ok, will use last attribute
2912 .segment "ZP2": absolute ; Error, redecl mismatch
2915 See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"
2916 name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref
2917 id=".RODATA" name=".RODATA"></tt>
2920 <sect1><tt>.SETCPU</tt><label id=".SETCPU"><p>
2922 Switch the CPU instruction set. The command is followed by a string that
2923 specifies the CPU. Possible values are those that can also be supplied to
2924 the <tt><ref id="option--cpu" name="--cpu"></tt> command line option,
2925 namely: 6502, 65SC02, 65C02, 65816 and sunplus. Please note that support
2926 for the sunplus CPU is not available in the freeware version, because the
2927 instruction set of the sunplus CPU is "proprietary and confidential".
2929 See: <tt><ref id=".CPU" name=".CPU"></tt>,
2930 <tt><ref id=".IFP02" name=".IFP02"></tt>,
2931 <tt><ref id=".IFP816" name=".IFP816"></tt>,
2932 <tt><ref id=".IFPC02" name=".IFPC02"></tt>,
2933 <tt><ref id=".IFPSC02" name=".IFPSC02"></tt>,
2934 <tt><ref id=".P02" name=".P02"></tt>,
2935 <tt><ref id=".P816" name=".P816"></tt>,
2936 <tt><ref id=".PC02" name=".PC02"></tt>,
2937 <tt><ref id=".PSC02" name=".PSC02"></tt>
2940 <sect1><tt>.SMART</tt><label id=".SMART"><p>
2942 Switch on or off smart mode. The command must be followed by a '+' or
2943 '-' character to switch the option on or off respectively. The default
2944 is off (that is, the assembler doesn't try to be smart), but this
2945 default may be changed by the -s switch on the command line.
2947 In smart mode the assembler will do the following:
2950 <item>Track usage of the <tt/REP/ and <tt/SEP/ instructions in 65816 mode
2951 and update the operand sizes accordingly. If the operand of such an
2952 instruction cannot be evaluated by the assembler (for example, because
2953 the operand is an imported symbol), a warning is issued. Beware: Since
2954 the assembler cannot trace the execution flow this may lead to false
2955 results in some cases. If in doubt, use the <tt/.Inn/ and <tt/.Ann/
2956 instructions to tell the assembler about the current settings.
2957 <item>In 65816 mode, replace a <tt/RTS/ instruction by <tt/RTL/ if it is
2958 used within a procedure declared as <tt/far/, or if the procedure has
2959 no explicit address specification, but it is <tt/far/ because of the
2967 .smart - ; Stop being smart
2970 See: <tt><ref id=".A16" name=".A16"></tt>,
2971 <tt><ref id=".A8" name=".A8"></tt>,
2972 <tt><ref id=".I16" name=".I16"></tt>,
2973 <tt><ref id=".I8" name=".I8"></tt>
2976 <sect1><tt>.STRUCT</tt><label id=".STRUCT"><p>
2978 Starts a struct definition. Structs are covered in a separate section named
2979 <ref id="structs" name=""Structs and unions"">.
2981 See: <tt><ref id=".ENDSTRUCT" name=".ENDSTRUCT"></tt>
2984 <sect1><tt>.SUNPLUS</tt><label id=".SUNPLUS"><p>
2986 Enable the SunPlus instructions set. This command will not work in the
2987 freeware version of the assembler, because the instruction set is
2988 "proprietary and confidential".
2990 See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02"
2991 name=".PSC02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt>, and
2992 <tt><ref id=".P816" name=".P816"></tt>
2995 <sect1><tt>.TAG</tt><label id=".TAG"><p>
2997 Allocate space for a struct or union.
3008 .tag Point ; Allocate 4 bytes
3012 <sect1><tt>.WARNING</tt><label id=".WARNING"><p>
3014 Force an assembly warning. The assembler will output a warning message
3015 preceeded by "User warning". This warning will always be output, even if
3016 other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt>
3017 command line option.
3019 This command may be used to output possible problems when assembling
3028 .warning "Forward jump in jne, cannot optimize!"
3038 See also the <tt><ref id=".ERROR" name=".ERROR"></tt> and <tt><ref id=".OUT"
3039 name=".OUT"></tt> directives.
3042 <sect1><tt>.WORD</tt><label id=".WORD"><p>
3044 Define word sized data. Must be followed by a sequence of (word ranged,
3045 but not necessarily constant) expressions.
3050 .word $0D00, $AF13, _Clear
3054 <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"><p>
3056 Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment.
3057 The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a
3061 .segment "ZEROPAGE", zeropage
3064 Because of the "zeropage" attribute, labels declared in this segment are
3065 addressed using direct addressing mode if possible. You <em/must/ instruct
3066 the linker to place this segment somewhere in the address range 0..$FF
3067 otherwise you will get errors.
3069 See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt>
3073 <sect>Macros<label id="macros"><p>
3076 <sect1>Introduction<p>
3078 Macros may be thought of as "parametrized super instructions". Macros are
3079 sequences of tokens that have a name. If that name is used in the source
3080 file, the macro is "expanded", that is, it is replaced by the tokens that
3081 were specified when the macro was defined.
3084 <sect1>Macros without parameters<p>
3086 In it's simplest form, a macro does not have parameters. Here's an
3090 .macro asr ; Arithmetic shift right
3091 cmp #$80 ; Put bit 7 into carry
3092 ror ; Rotate right with carry
3096 The macro above consists of two real instructions, that are inserted into
3097 the code, whenever the macro is expanded. Macro expansion is simply done
3098 by using the name, like this:
3107 <sect1>Parametrized macros<p>
3109 When using macro parameters, macros can be even more useful:
3123 When calling the macro, you may give a parameter, and each occurence of
3124 the name "addr" in the macro definition will be replaced by the given
3143 A macro may have more than one parameter, in this case, the parameters
3144 are separated by commas. You are free to give less parameters than the
3145 macro actually takes in the definition. You may also leave intermediate
3146 parameters empty. Empty parameters are replaced by empty space (that is,
3147 they are removed when the macro is exanded). If you have a look at our
3148 macro definition above, you will see, that replacing the "addr" parameter
3149 by nothing will lead to wrong code in most lines. To help you, writing
3150 macros with a variable parameter list, there are some control commands:
3152 <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and
3153 returns true, if there are any tokens on the remainder of the line. Since
3154 empty parameters are replaced by nothing, this may be used to test if a given
3155 parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the
3158 Look at this example:
3161 .macro ldaxy a, x, y
3174 This macro may be called as follows:
3177 ldaxy 1, 2, 3 ; Load all three registers
3179 ldaxy 1, , 3 ; Load only a and y
3181 ldaxy , , 3 ; Load y only
3184 There's another helper command for determining, which macro parameters are
3185 valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is
3186 replaced by the parameter count given, <em/including/ intermediate empty macro
3190 ldaxy 1 ; .PARAMCOUNT = 1
3191 ldaxy 1,,3 ; .PARAMCOUNT = 3
3192 ldaxy 1,2 ; .PARAMCOUNT = 2
3193 ldaxy 1, ; .PARAMCOUNT = 2
3194 ldaxy 1,2,3 ; .PARAMCOUNT = 3
3198 <sect1>Detecting parameter types<p>
3200 Sometimes it is nice to write a macro that acts differently depending on the
3201 type of the argument supplied. An example would be a macro that loads a 16 bit
3202 value from either an immediate operand, or from memory. The <tt/<ref
3203 id=".MATCH" name=".MATCH">/ and <tt/<ref id=".XMATCH" name=".XMATCH">/
3204 functions will allow you to do exactly this:
3208 .if (.match (.left (1, arg), #))
3210 lda #<(.right (.tcount (arg)-1, arg))
3211 ldx #>(.right (.tcount (arg)-1, arg))
3213 ; assume absolute or zero page
3220 Using the <tt/<ref id=".MATCH" name=".MATCH">/ function, the macro is able to
3221 check if its argument begins with a hash mark. If so, two immediate loads are
3222 emitted, Otherwise a load from an absolute zero page memory location is
3223 assumed. So this macro can be used as
3228 ldax #$1234 ; X=$12, A=$34
3230 ldax foo ; X=$56, A=$78
3234 <sect1>Recursive macros<p>
3236 Macros may be used recursively:
3239 .macro push r1, r2, r3
3248 There's also a special macro to help writing recursive macros: <tt><ref
3249 id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion
3253 .macro push r1, r2, r3, r4, r5, r6, r7
3255 ; First parameter is empty
3261 push r2, r3, r4, r5, r6, r7
3265 When expanding this macro, the expansion will push all given parameters
3266 until an empty one is encountered. The macro may be called like this:
3269 push $20, $21, $32 ; Push 3 ZP locations
3270 push $21 ; Push one ZP location
3274 <sect1>Local symbols inside macros<p>
3276 Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and
3277 <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need?
3278 Have a look at the inc16 macro above. Here is it again:
3292 If you have a closer look at the code, you will notice, that it could be
3293 written more efficiently, like this:
3304 But imagine what happens, if you use this macro twice? Since the label
3305 "Skip" has the same name both times, you get a "duplicate symbol" error.
3306 Without a way to circumvent this problem, macros are not as useful, as
3307 they could be. One solution is, to start a new lexical block inside the
3321 Now the label is local to the block and not visible outside. However,
3322 sometimes you want a label inside the macro to be visible outside. To make
3323 that possible, there's a new command that's only usable inside a macro
3324 definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one
3325 or more symbols as local to the macro expansion. The names of local variables
3326 are replaced by a unique name in each separate macro expansion. So we could
3327 also solve the problem above by using <tt/.LOCAL/:
3331 .local Skip ; Make Skip a local symbol
3338 Skip: ; Not visible outside
3343 <sect1>C style macros<p>
3345 Starting with version 2.5 of the assembler, there is a second macro type
3346 available: C style macros using the <tt/.DEFINE/ directive. These macros are
3347 similar to the classic macro type described above, but behaviour is sometimes
3352 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not
3353 span more than a line. You may use line continuation (see <tt><ref
3354 id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over
3355 more than one line for increased readability, but the macro itself
3356 may not contain an end-of-line token.
3358 <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share
3359 the name space with classic macros, but they are detected and replaced
3360 at the scanner level. While classic macros may be used in every place,
3361 where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE"
3362 name=".DEFINE"></tt> style macros are allowed anywhere in a line. So
3363 they are more versatile in some situations.
3365 <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take
3366 parameters. While classic macros may have empty parameters, this is
3367 not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros.
3368 For this macro type, the number of actual parameters must match
3369 exactly the number of formal parameters.
3371 To make this possible, formal parameters are enclosed in braces when
3372 defining the macro. If there are no parameters, the empty braces may
3375 <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not
3376 contain end-of-line tokens, there are things that cannot be done. They
3377 may not contain several processor instructions for example. So, while
3378 some things may be done with both macro types, each type has special
3379 usages. The types complement each other.
3383 Let's look at a few examples to make the advantages and disadvantages
3386 To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the
3387 following <tt/.DEFINE/:
3392 foo EQU $1234 ; This is accepted now
3395 You may use the directive to define string constants used elsewhere:
3398 ; Define the version number
3399 .define VERSION "12.3a"
3405 Macros with parameters may also be useful:
3408 .define DEBUG(message) .out message
3410 DEBUG "Assembling include file #3"
3413 Note that, while formal parameters have to be placed in braces, this is
3414 not true for the actual parameters. Beware: Since the assembler cannot
3415 detect the end of one parameter, only the first token is used. If you
3416 don't like that, use classic macros instead:
3424 (This is an example where a problem can be solved with both macro types).
3427 <sect1>Characters in macros<p>
3429 When using the <ref id="option-t" name="-t"> option, characters are translated
3430 into the target character set of the specific machine. However, this happens
3431 as late as possible. This means that strings are translated if they are part
3432 of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ"
3433 name=".ASCIIZ"></tt> command. Characters are translated as soon as they are
3434 used as part of an expression.
3436 This behaviour is very intuitive outside of macros but may be confusing when
3437 doing more complex macros. If you compare characters against numeric values,
3438 be sure to take the translation into account.
3443 <sect>Macro packages<label id="macropackages"><p>
3445 Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined
3446 macro packages may be included with just one command. Available macro packages
3450 <sect1><tt>.MACPACK generic</tt><p>
3452 This macro package defines macros that are useful in almost any program.
3453 Currently, two macros are defined:
3468 <sect1><tt>.MACPACK longbranch</tt><p>
3470 This macro package defines long conditional jumps. They are named like the
3471 short counterpart but with the 'b' replaced by a 'j'. Here is a sample
3472 definition for the "<tt/jeq/" macro, the other macros are built using the same
3477 .if .def(Target) .and ((*+2)-(Target) <= 127)
3486 All macros expand to a short branch, if the label is already defined (back
3487 jump) and is reachable with a short jump. Otherwise the macro expands to a
3488 conditional branch with the branch condition inverted, followed by an absolute
3489 jump to the actual branch target.
3491 The package defines the following macros:
3494 jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc
3499 <sect1><tt>.MACPACK cbm</tt><p>
3501 The cbm macro package will define a macro named <tt/scrcode/. It takes a
3502 string as argument and places this string into memory translated into screen
3506 <sect1><tt>.MACPACK cpu</tt><p>
3508 This macro package does not define any macros but constants used to examine
3509 the value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable. For
3510 each supported CPU a constant similar to
3520 is defined. These constants may be used to determine the exact type of the
3521 currently enabled CPU. In addition to that, for each CPU instruction set,
3522 another constant is defined:
3532 The value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable may
3533 be checked with <tt/<ref id="operators" name=".BITAND">/ to determine if the
3534 currently enabled CPU supports a specific instruction set. For example the
3535 65C02 supports all instructions of the 65SC02 CPU, so it has the
3536 <tt/CPU_ISET_65SC02/ bit set in addition to its native <tt/CPU_ISET_65C02/
3540 .if (.cpu .bitand CPU_ISET_65SC02)
3548 it is possible to determine if the
3554 instruction is supported, which is the case for the 65SC02, 65C02 and 65816
3555 CPUs (the latter two are upwards compatible to the 65SC02).
3559 <sect>Structs and unions<label id="structs"><p>
3561 Structs and unions are special forms of <ref id="scopes" name="scopes">. They
3562 are to some degree comparable to their C counterparts. Both have a list of
3563 members. Each member allocates storage and may optionally have a name, which,
3564 in case of a struct, is the offset from the beginning and, in case of a union,
3567 Here is an example for a very simple struct with two members and a total size
3577 A union shares the total space between all its members, its size is the same
3578 as that of the largest member.
3580 A struct or union must not necessarily have a name. If it is anonymous, no
3581 local scope is opened, the identifiers used to name the members are placed
3582 into the current scope instead.
3584 A struct may contain unnamed members and definitions of local structs. The
3585 storage allocators may contain a multiplier, as in the example below:
3590 .word 2 ; Allocate two words
3596 Using the <ref id=".TAG" name=".TAG"> keyword, it is possible to embedd
3597 already defined structs or unions in structs:
3611 Space for a struct or union may be allocated using the <ref id=".TAG"
3612 name=".TAG"> directive.
3618 Currently, members are just offsets from the start of the struct or union. To
3619 access a field of a struct, the member offset has to be added to the address
3620 of the struct itself:
3623 lda C+Circle::Radius ; Load circle radius into A
3626 This may change in a future version of the assembler.
3629 <sect>Module constructors/destructors<label id="condes"><p>
3631 <em>Note:</em> This section applies mostly to C programs, so the explanation
3632 below uses examples from the C libraries. However, the feature may also be
3633 useful for assembler programs.
3636 <sect1>Module overview<p>
3638 Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
3639 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> keywords it it possible to export
3640 functions in a special way. The linker is able to generate tables with all
3641 functions of a specific type. Such a table will <em>only</em> include symbols
3642 from object files that are linked into a specific executable. This may be used
3643 to add initialization and cleanup code for library modules.
3645 The C heap functions are an example where module initialization code is used.
3646 All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few
3647 variables that contain the start and the end of the heap, pointers to the free
3648 list and so on. Since the end of the heap depends on the size and start of the
3649 stack, it must be initialized at runtime. However, initializing these
3650 variables for programs that do not use the heap are a waste of time and
3653 So the central module defines a function that contains initialization code and
3654 exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if)
3655 this module is added to an executable by the linker, the initialization
3656 function will be placed into the table of constructors by the linker. The C
3657 startup code will call all constructors before <tt/main/ and all destructors
3658 after <tt/main/, so without any further work, the heap initialization code is
3659 called once the module is linked in.
3661 While it would be possible to add explicit calls to initialization functions
3662 in the startup code, the new approach has several advantages:
3666 If a module is not included, the initialization code is not linked in and not
3667 called. So you don't pay for things you don't need.
3670 Adding another library that needs initialization does not mean that the
3671 startup code has to be changed. Before we had module constructors and
3672 destructors, the startup code for all systems had to be adjusted to call the
3673 new initialization code.
3676 The feature saves memory: Each additional initialization function needs just
3677 two bytes in the table (a pointer to the function).
3682 <sect1>Calling order<p>
3684 Both, constructors and destructors are sorted in increasing priority order by
3685 the linker when using one of the builtin linker configurations, so the
3686 functions with lower priorities come first and are followed by those with
3687 higher priorities. The C library runtime subroutine that walks over the
3688 constructor and destructor tables calls the functions starting from the top of
3689 the table - which means that functions with a high priority are called first.
3691 So when using the C runtime, both constructors and destructors are called with
3692 high priority functions first, followed by low priority functions.
3697 When creating and using module constructors and destructors, please take care
3703 The linker will only generate function tables, it will not generate code to
3704 call these functions. If you're using the feature in some other than the
3705 existing C environments, you have to write code to call all functions in a
3706 linker generated table yourself. See the <tt>condes</tt> module in the C
3707 runtime for an example on how to do this.
3710 The linker will only add addresses of functions that are in modules linked to
3711 the executable. This means that you have to be careful where to place the
3712 condes functions. If initialization is needed for a group of functions, be
3713 sure to place the initialization function into a module that is linked in
3714 regardless of which function is called by the user.
3717 The linker will generate the tables only when requested to do so by the
3718 <tt/FEATURE CONDES/ statement in the linker config file. Each table has to
3719 be requested separately.
3722 Constructors and destructors may have priorities. These priorities determine
3723 the order of the functions in the table. If your intialization or cleanup code
3724 does depend on other initialization or cleanup code, you have to choose the
3725 priority for the functions accordingly.
3728 Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref
3729 id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> statements, there is also a more
3730 generic command: <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to
3731 specify an additional type. Predefined types are 0 (constructor) and 1
3732 (destructor). The linker generates a separate table for each type on request.
3737 <sect>Porting sources from other assemblers<p>
3739 Sometimes it is necessary to port code written for older assemblers to ca65.
3740 In some cases, this can be done without any changes to the source code by
3741 using the emulation features of ca65 (see <tt><ref id=".FEATURE"
3742 name=".FEATURE"></tt>). In other cases, it is necessary to make changes to the
3745 Probably the biggest difference is the handling of the <tt><ref id=".ORG"
3746 name=".ORG"></tt> directive. ca65 generates relocatable code, and placement is
3747 done by the linker. Most other assemblers generate absolute code, placement is
3748 done within the assembler and there is no external linker.
3750 In general it is not a good idea to write new code using the emulation
3751 features of the assembler, but there may be situations where even this rule is
3756 You need to use some of the ca65 emulation features to simulate the behaviour
3757 of such simple assemblers.
3760 <item>Prepare your sourcecode like this:
3763 ; if you want TASS style labels without colons
3764 .feature labels_without_colons
3766 ; if you want TASS style character constants
3767 ; ("a" instead of the default 'a')
3768 .feature loose_char_term
3770 .word *+2 ; the cbm load address
3775 notice that the two emulation features are mostly useful for porting
3776 sources originally written in/for TASS, they are not needed for the
3777 actual "simple assembler operation" and are not recommended if you are
3778 writing new code from scratch.
3780 <item>Replace all program counter assignments (which are not possible in ca65
3781 by default, and the respective emulation feature works different from what
3782 you'd expect) by another way to skip to another memory location, for example
3783 the <tt><ref id=".RES" name=".RES"></tt>directive.
3787 .res $2000-* ; reserve memory up to $2000
3790 notice that other than the original TASS, ca65 can never move the
3791 programmcounter backwards - think of it as if you are assembling to disc with
3794 <item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.goto/ etc.) must be
3795 rewritten to match ca65 syntax. Most importantly notice that due to the lack
3796 of <tt/.goto/, everything involving loops must be replaced by
3797 <tt><ref id=".REPEAT" name=".REPEAT"></tt>.
3799 <item>To assemble code to a different address than it is executed at, use the
3800 <tt><ref id=".ORG" name=".ORG"></tt> directive instead of
3801 <tt/.offs/-constructs.
3808 .reloc ; back to normal
3811 <item>Then assemble like this:
3814 cl65 --start-addr 0x0ffe -t none myprog.s -o myprog.prg
3817 notice that you need to use the actual start address minus two, since two
3818 bytes are used for the cbm load address.
3823 <sect>Bugs/Feedback<p>
3825 If you have problems using the assembler, if you find any bugs, or if
3826 you're doing something interesting with the assembler, I would be glad to
3827 hear from you. Feel free to contact me by email
3828 (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">).
3834 ca65 (and all cc65 binutils) are (C) Copyright 1998-2003 Ullrich von
3835 Bassewitz. For usage of the binaries and/or sources the following
3836 conditions do apply:
3838 This software is provided 'as-is', without any expressed or implied
3839 warranty. In no event will the authors be held liable for any damages
3840 arising from the use of this software.
3842 Permission is granted to anyone to use this software for any purpose,
3843 including commercial applications, and to alter it and redistribute it
3844 freely, subject to the following restrictions:
3847 <item> The origin of this software must not be misrepresented; you must not
3848 claim that you wrote the original software. If you use this software
3849 in a product, an acknowledgment in the product documentation would be
3850 appreciated but is not required.
3851 <item> Altered source versions must be plainly marked as such, and must not
3852 be misrepresented as being the original software.
3853 <item> This notice may not be removed or altered from any source
projects / cc65 / blob