
DOCUMENTATION FOR DASM, a high level macro cross assembler for:

	-6502 (and 6507)
	-68705
	-6803
	-HD6303 (extension of 6803)
	-68HC11


ABSTRACT

    This file contains the main documentation for DASM. It explains how
    to use Dasm and what the supported assembler directives are.

    DASM's homepage is https://dasm-assembler.github.io/ since release
    2.20.12.


LEGALESE

    the DASM macro assembler (aka small systems cross assembler)

    Copyright (c) 1988-2002 by Matthew Dillon.
    Copyright (c) 1995 by Olaf "Rhialto" Seibert.
    Copyright (c) 2003-2008 by Andrew Davie.
    Copyright (c) 2008 by Peter H. Froehlich.
	Copyright (c) 2019-2026 by the DASM team.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.


PREFACE FROM MATT:

    Over the last year my work has included writing software to drive small
    single-chip microcomputers for various things (remote telemetry units,
    for instance).  I have had need to program quite a few different
    processors over that time.

    At the beginning, I used an awful macro assembler running on an IBM-PC.
    I *really* wanted to do it on my Amiga.  Thus the writing of this
    program.

    Feel free to suggest other similar processors for me to add to the list!
    The processor type is specified with a pseudo-op (see below).  This
    assembler produces only binary output in one of three formats described
    below.  In general, one has a master assembly file which INCLUDEs all
    the modules.

    Also provided is FTOHEX which converts an output file in one of the
    three formats to an intel-hex format suitable for many intelligent
    prom programmers (I have a GTEK).

    YES it's packed with features!

FEATURES:

    -fast assembly
    -supports several common 8 bit processor models (NOT 8086, thank god!)
    -takes as many passes as needed
    -automatic checksum generation, special symbol '...'
    -several binary output formats available.  Format 2 allows reverse
     indexed origins.
    -multiple segments, BSS segments (no generation), relocatable origin.
    -expressions, as in C but [] is used instead of () for parenthesis.
     (all expressions are computed with 32 bit integers)
    -no real limitation on label size, label values are 32 bits.
    -complex pseudo ops, repeat loops, macros, etc....


PREFACE FROM ANDREW (APRIL/2003)

    The documentation is lagging a bit behind the modifications.
    Essentially the information contained herein is correct, but
    there have been minor changes to the formatting of output data.

    Please see the accompanying text files in the distribution's
    root directory for a list of recent changes to DASM.


PREFACE FROM PETER (APRIL/2008)
    
    Everything Andrew says above is still true, there have been a
    few sporadic updates to the documentation but no major ones,
    not even Olaf Seibert's changes from 1995 have been integrated,
    to say nothing of Thomas Mathys' F8 backend from 2004. We are
    urgently looking for volunteers to help with the documentation!


COMMAND LINE:

	dasm sourcefile [options]

	options:    -f#     output format 1-3 (default 1, see below)
		    -oname  output file name (else a.out)
		    -lname  list file name (else none generated) 
		    -Lname  list file name, containing all passes
		    -sname  symbol dump file name (else none generated)
		    -v#     verboseness 0-4 (default 0, see below)
		    -d      debug mode (for developers)
		    -Dsymbol		define symbol, set to 0
		    -Dsymbol=expression	define symbol, set to expression
		    -Msymbol=expression	define symbol using EQM (same as -D)
		    -Idir   search directory for include and incbin
		    -p#     maximum number of passes
		    -P#     maximum number of passes, with fewer checks
		    -T#     symbol table sorting (default 0 = alphabetical,
			    1 = address/value)
		    -E#     error format (default 0 = MS, 1 = Dillon, 2 = GNU)
		    -S      strict syntax checking

	Example:    dasm master.asm -f2 -oout -llist -v3 -DVER=4

Note:	A slash (/) or dash (-) must prefix options.


Return Value:

	The assembler will return 0 on successful compilation, 1 otherwise.


FORMAT OPTIONS:

    1  (DEFAULT)

	The output file contains a two byte origin in LSB,MSB order, then
	data until the end of the file.

	Restrictions:	Any instructions which generate output (within an
	initialized segment) must do so with an ascending PC.  Initialized
	segments must occur in ascending order.

    2  RAS (Random Access Segment)

	The output file contains one or more hunks.  Each hunk consists
	of a 2 byte origin (LSB,MSB), 2 byte length (LSB,MSB), and that
	number of data bytes.  The hunks occur in the same order as
	initialized segments in the assembly.  There are no restrictions
	to segment ordering (i.e. reverse indexed ORG statements are
	allowed).  The next hunk begins after the previous hunk's data,
	until the end of the file.

    3  RAW (Raw)

	The output file contains data only (format #1 without the 2 byte
	header).  Restrictions are the same as for format #1.

	Format 3    RAW (Raw format)
	    Same as format 1, but NO header origin is generated.  You get
	    nothing but data.

VERBOSE OPTIONS:

    0	(default)

	Only warnings and errors are generated

    1
	-Segment list information generated after each pass
	-Include file names are displayed
	-statistics on why the assembler is going to make another pass
	    R1,R2 reason code: R3
	    where R1 is the number of times the assembler encountered
	    something requiring another pass to resolve.  R2 is the
	    number of references to unknown symbols which occurred in the
	    pass (but only R1 determines the need for another pass).  R3
	    is a BITMASK of the reasons why another pass is required.
	    See the end of this document for bit designations.

    2
	mismatches between program labels and equates are displayed
	on every pass (usually none occur in the first pass unless you
	have re-declared a symbol name).

	displayed information for symbols:
	    ???? = unknown value
	    str  = symbol is a string
	    eqm  = symbol is an eqm macro
	    (r)  = symbol has been referenced
	    (s)  = symbol created with SET or EQM pseudo-op

    3
	    Unresolved and unreferenced symbols are displayed every pass
	    (unsorted, sorry)

    4
	    An entire symbol list is displayed every pass to STDOUT.
	    (unsorted, sorry)



PROCESSOR MODEL:

    The processor model is chosen with the PROCESSOR pseudo-op and should
    be the first thing you do in your assembly file.   Different processor
    models use different integer formats (see below).  The word order does
    not effect the headers in the output files (-f1 and -f2), which are
    always LSB,MSB.  The word ordering effects all address, word, and
    long generation.

    Only one PROCESSOR pseudo-op may be declared in the entire assembly,
    and should be the first thing encountered.

	-6502	    LSB,MSB
	-68HC11     MSB,LSB
	-68705	    MSB,LSB
	-6803	    MSB,LSB
	-HD6303     MSB,LSB
	-F8         ?

SEGMENTS:
    The SEG pseudo-op creates/sets the current segment.  Each segment has
    it's own origin and is optionally an 'uninitialized' segment.
    Uninitialized segments produce no output and have no restrictions.  This
    is useful for determining the size of a certain assembly sequence
    without generating code, and for assigning RAM to labels.

    'Initialized' segments produce output.  The following should be
    considered when generating roms:

    (1) The default fill character when using ORG (and format 1 or 3) to
	skip forward is 00.  This is a GLOBAL default and effects all
	segments.  See ORG.

    (2) The default fill character for DS is 00 and is independent of
	the default fill character for ORG (see DS).

GENERAL:
    Most everything is recursive.  You cannot have a macro DEFINITION
    within a macro definition, but can nest macro calls, repeat loops,
    and include files.

    The other major feature in this assembler is the SUBROUTINE pseudo-op,
    which logically separates local labels (starting with a dot).  This
    allows you to reuse label names (for example, .1 .fail) rather than
    think up crazy combinations of the current subroutine to keep it all
    unique.

    Almost nothing need be resolved in pass 1.	The assembler will make
    multiple passes in an attempt to resolve the assembly (including just
    one pass if everything is resolved immediately).


PSEUDOPS:

	INCLUDE     "name"

	    Include another assembly file.

[label] INCBIN	    "name" [,SkipBytes]

	    Include another file literally in the output.

		If provided with the second argument, the first <SkipBytes>
		bytes of the file will be excluded. This can be useful for
		skipping unwanted headers, e. g. load address indicators,
		SID tune headers, etc.

	INCDIR	    "directory name"

	    Add the given directory name to the list of places where
	    INCLUDE and INCBIN search their files. First, the names are
	    tried relative to the current directory, if that fails and
	    the name is not an absolute pathname, the list is tried.
	    You can optionally end the name with a /. AmigaDOS filename
	    conventions imply that two slashes at the
	    end of an INCDIR (dir//) indicates the parent directory, and
	    so does an INCLUDE /filename.

	    The command-line option -Idir is equivalent to an INCDIR
	    directive placed before the source file.

	    Currently the list is not cleared between passes, but each
	    exact directory name is added to the list only once.
	    This may change in subsequent releases.

[label] SEG[.U]     name

	    This sets the current segment, creating it if necessary.  If
	    a .U extension is specified on segment creation, the segment
	    is an UNINITIALIZED segment.  The .U is not needed when going
	    back to an already created uninitialized segment, though it
	    makes the code more readable.

[label] DC[.BWL]    exp,exp,exp ...

	    Declare data in the current segment.  No output is generated if
	    within a .U segment.  Note that the byte ordering for the
	    selected processor is used for each entry.

	    The default size extension is a byte.

	    BYTE, WORD and LONG are synonyms for DC.B, DC.W and DC.L.

[label] DS[.BWL]    exp[,filler]

	    declare space (default filler is 0). Data is not generated if
	    within an uninitialized segment.  Note that the number of bytes
	    generated is exp * entrysize (1,2, or 4)

	    The default size extension is a byte.

	    Note that the default filler is always 0 (has nothing to do
	    with the ORG default filler).

[label] DV[.BWL]    eqmlabel exp,exp,exp....

	    This is equivalent to DC, but each exp in the list is passed
	    through the symbolic expression specified by the EQM label.
	    The expression is held in a special symbol dotdot '..' on each
	    call to the EQM label.

	    See EQM below

[label] HEX	    hh hh hh..

	    This sets down raw HEX data.  Spaces are optional between bytes.
	    NO EXPRESSIONS are allowed.  Note that you do NOT place a $
	    in front of the digits.  This is a short form for creating
	    tables compactly.  Data is always laid down on a byte-by-byte
	    basis.

	    Example:	    HEX 1A45 45 13254F 3E12

	ERR

	    Abort assembly.

[label] ORG	    exp[,DefaultFillVal]

	    This pseudop sets the current origin.  You can also set the
	    global default fill character (a byte value) with this
	    pseudoop.  NOTE that no filler is generated until the first
	    data-generating opcode/psueoop is encountered after this one.
	    Sequences like:

		org  0,255
		org  100,0
		org  200
		dc   23

	    will result in 200 zero's and a 23. This allows you to specify
	    some ORG, then change your mind and specify some other (lower
	    address) ORG without causing an error (assuming nothing is
	    generated in between).

	    Normally, DS and ALIGN are used to generate specific filler
	    values.

[label] RORG	    exp

	    This activates the relocatable origin.  All generated
	    addresses, including '.', although physically placed at the
	    true origin, will use values from the relocatable origin.
	    While in effect both the physical origin and relocatable origin
	    are updated.

	    The relocatable origin can skip around (no limitations).  The
	    relocatable origin is a function of the segment.  That is, you
	    can still SEG to another segment that does not have a
	    relocatable origin activated, do other (independent) stuff
	    there, and then switch back to the current segment and continue
	    where you left off.

	PROCESSOR model

	    do not quote.  model is one of: 6502,6803,HD6303,68705,68HC11,F8
	    Can only be executed once, and should be the first thing
	    encountered by the assembler.

	ECHO exp,exp,exp

	    The expressions (which may also be strings), are echoed on the
	    screen and into the list file.

[label] REND

	    Deactivate the relocatable origin for the current segment.
	    Generation uses the real origin for reference.

[label] ALIGN	    N[,fill]

	    Align the current PC to an N byte boundary.	The default
	    fill character is always 0, and has nothing to do with
	    the default fill character specifiable in an ORG.

[label] SUBROUTINE  name

	    This isn't really a subroutine, but a boundary between sets of
	    temporary labels (which begin with a dot).	Temporary label
	    names are unique within segments of code bounded by SUBROUTINE:

		CHARLIE subroutine
			ldx #10
		.1	dex
			bne .1
		BEN	subroutine
			ldx #20
		.qq	dex
			bne .qq

	    Automatic temporary label boundaries occur for each macro level.
	    Usually temporary labels are used in macros and within actual
	    subroutines (so you don't have to think up a thousand different
	    names)


symbol	EQU	    exp

symbol	=	    exp

	    The expression is evaluated and the result assigned to the
	    symbol.

	    If this option is enabled, you can use the common idiom of

		. EQU . + 3	(or . = .+3)

	    in other words, you can assign to "." (or "*" if OlafStar
	    is also enabled) instead of an ORG or RORG directive.
	    More formally, a directive of the form ". EQU expr" is
	    interpreted as if it were written " (R)ORG expr".
	    The RORG is used if a relocatable origin is already in effect,
	    otherwise ORG is used. Note that the first example is NOT
	    equivalent with "DS.B 3" when the rorg is in effect.

symbol	EQM	    exp

	    The STRING representing the expression is assigned to the
	    symbol.  Occurrences of the label in later expressions causes
	    the string to be evaluated for each occurrence.  Also used in
	    conjunction with the DV psuedo-op.

symbol	SET	    exp

	    Same as EQU, but the symbol may be reassigned later.

symbol	SETSTR	    exp

	    The expression is converted to a string, and assigned to the
	    symbol. Typical use case is within a macro, to allow the
	    macro to echo or otherwise use the name of an argument.

	MAC	    name

	    Declare a macro.  lines between MAC and ENDM are the macro.
	    You cannot recursively declare a macro.  You CAN recursively
	    use a macro (reference a macro in a macro).  No label is
	    allowed to the left of MAC or ENDM.

	    Arguments passed to macros are referenced with: {#}.  The first
	    argument passed to a macro would thus be {1}.  You should
	    always use LOCAL labels (.name) inside macros which you use
	    more than once. {0} represents an EXACT substitution of the
	    ENTIRE argument line.

	ENDM

	    end of macro def.  NO LABEL ALLOWED ON THE LEFT!

	MEXIT

	    Used in conjunction with conditionals.  Exits the current macro
	    level.

[label] IFCONST     exp

	    Is TRUE if the expression result is defined,  FALSE otherwise
	    and NO error is generated if the expression is undefined.

[label] IFNCONST    exp

	    Is TRUE if the expression result is undefined, FALSE otherwise
	    and NO error is generated if the expression is undefined.

[label] IF	    exp

	    Is TRUE if the expression result is defined AND non-zero.
	    Is FALSE if the expression result is defined AND zero.
	    Neither IF or ELSE will be executed if the expression result
	    is undefined.  If the expression is undefined, another assembly
	    pass is automatically taken.

	    If this happens, phase errors in the next pass only will not
	    be reported unless the verboseness is 1 or more.

[label] ELSE

	    ELSE the current IF.

[label] ENDIF
[label] EIF

	    Terminate an IF. ENDIF and EIF are equivalent.

[label] REPEAT	    exp
[label] REPEND

	    Repeat code between REPEAT/REPEND 'exp' times.

#if DAD
  		if exp == 0,
	    the code repeats forever.  exp is evaluated once.

		If exp == 0, the repeat loop is ignored.
		If exp < 0, a warning "REPEAT parameter < 0 (ignored)" is generated 		and the repeat loop is ignored.
#endif
		
		Y   SET     0
		    REPEAT  10
		X   SET     0
		    REPEAT  10
		    DC	    X,Y
		X   SET     X + 1
		    REPEND
		Y   SET     Y + 1
		    REPEND

	    generates an output table:	0,0 1,0 2,0 ... 9,0  0,1 1,1 2,1
	    ... 9,1, etc...

	    Labels within a REPEAT/REPEND should be temporary labels with a
	    SUBROUTINE pseudo-op to keep them unique.

	    The Label to the left of REPEND is assigned AFTER the loop
	    FINISHES.


[label] XXX[.force] operand

	    XXX is some mnemonic, not necessarily three characters long.
	    The .FORCE optional extension is used to force specific
	    addressing modes (see below).

[label] LIST ON or OFF

	    Globally turns listing on or off, starting with the current
	    line.

	    When you give LOCALON or LOCALOFF the effect is local to the
	    current macro or included file. For a line to be listed both
	    the global and local list switches must be on.

	All pseudo-ops (and incidentally also the mnemonics) can be
	prefixed with a . for compatibility with other assemblers.
	So .IF is the same as IF. This works only because lone .FORCE
	extensions are meaningless.

GENERAL:

    The label will be set to the current ORG/RORG either before or after
    a pseudo-op is executed.  Most of the time, the label to the left of a
    pseudo-op is the current ORG/RORG. The following pseudo-op's labels are
    created AFTER execution of the pseudo-op:

	SEG, ORG, RORG, REND, ALIGN

EXTENSIONS:

    FORCE extensions are used to force an addressing mode.  In some cases,
    you can optimize the assembly to take fewer passes by telling it the
    addressing mode.  Force extensions are also used with DS,DC, and DV
    to determine the element size.  NOT ALL EXTENSIONS APPLY TO ALL
    PROCESSORS!

	example:    lda.z   charlie

	i   -implied
	ind -indirect word
	0   -implied
	0x  -implied indexing (0,x)
	0y  -implied indexing (0,y)
	b   -byte address
	bx  -byte address indexed x
	by  -byte address indexed y
	w   -word address
	wx  -word address indexed x
	wy  -word address indexed y
	l   -longword (4 bytes) (DS/DC/DV)
	r   -relative
	u   -uninitialized (SEG)

	First character equivalent substitutions:

	b z d	    (byte, zeropage, direct)
	w e a	    (word, extended, absolute)


ASSEMBLER PASSES:
    The assembler may have to make several passes through the source
    code to resolve all generation.  The number of passes is not
    limited to two.  Since this may result in an unexpected, verbose
    option 2, 3, and 4 have been provided to allow determination of the
    cause. The assembler will give up if it thinks it can't do the
    assembly in *any* number of passes.

    Error reporting could be better....

    The check if another pass might resolve the source is pretty good, but
    not perfect. You can specify the maximum number of passes to do
    (default -p10), and with the -P option you can override the normal check.
    This allows the following contrived example to resolve in 12 passes:

	org 1
	repeat [[x < 11] ? [x-11]] + 11
	dc.b	x
	repend
    x:

EXPRESSIONS:
	[] may be used to group expressions.  The precedense of operators
	is the same as for the C language in almost all respects.  Use
	brackets [] when you are unsure.  The reason () cannot be used to
	group expressions is due to a conflict with the 6502 and other
	assembly languages.

	It is possible to use () instead of [] in expressions following
	pseudo-ops, but not following mnemonics. So this works:
	if target & (pet3001 | pet4001), but this doesn't:
	lda #target & (pet3001 | pet4001).

	Some operators, such as ||, can return a resolved value even if
	one of the expressions is not resolved.   Operators are as follows:

	NOTE WELL!  Some operations will result in non-byte values when a
	byte value was wanted.	For example:	~1  is NOT $FF, but
	$FFFFFFFF.  Preceding it with a < (take LSB of) will solve the
	problem.  ALL ARITHMETIC IS CARRIED OUT IN 32 BITS.  The final
	Result will be automatically truncated to the maximum handleable
	by the particular machine language (usually a word) when applied
	to standard mnemonics.

	prec	    UNARY

	20  ~exp    one's complement.
	20  -exp    negation
	20  !exp    not expression (returns 0 if exp non-zero, 1 if exp zero)
	20  <exp    take LSB byte of a 16 bit expression
	20  >exp    take MSB byte of an expression

		    BINARY

	19  *	    multiplication
	19  /	    division
	19  %	    mod
	18  +	    addition
	18  -	    subtraction
	17  >>,<<   shift right, shift left
	16  >,>=    greater, greater equal
	16  <,<=    smaller, smaller equal
	15  ==	    equal to.  Try to use this instead of =
	15  =	    exactly the same as == (exists compatibility)
	15  !=	    not equal to
	14  &	    logical and
	13  ^	    logical xor
	12  |	    logical or
	11  &&	    left expression is true AND right expression is true
	10  ||	    left expression is true OR right expression is true
	 9  ?	    if left expression is true, result is right expression,
		    else result is 0.	[10 ? 20] returns 20
	 8  []	    group expressions
	 7  ,	    separate expressions in list (also used in
		    addressing mode resolution, BE CAREFUL!

    Note: The effect of the C conditional operator a ? b : c can be
    had with [a ? b - c] + c.

    Constants:

	nnn	decimal
	0nnn	octal
	%nnn	binary
	$nnn	hex
	'c      character
	"cc.."  string (NOT zero terminated if in DC/DS/DV)
	[exp]d	the constant expressions is evaluated and it's decimal
		result turned into an ascii string.

    Symbols:

	...	-holds CHECKSUM so far (of actual-generated stuff)
	..	-holds evaluated value in DV pseudo op
	.name	-represents a temporary symbol name.  Temporary symbols
		 may be reused inside MACROS and between SUBROUTINES, but
		 may not be referenced across macros or across SUBROUTINEs.
	.	-current program counter (as of the beginning of the
		 instruction).
	name	-beginning with an alpha character and containing letters,
		 numbers, or '_'.  Represents some global symbol name.
	*	-synonym for ., when not confused as an operator.
	nnn$	-temporary label, much like .name, except that defining
		 a non-temporary label has the effect that SUBROUTINE
		 has on .name.	They are unique within macros, like
		 .name.  Note that 0$ and 00$ are distinct, as are 8$
		 and 010$.
		 (mainly for compatibility with other assemblers.)

Dynamic Symbol/Labels

	When used in a symbol name, the "," operator indicates one or more
	arguments that follow should be evaluated, and the resulting values 
	should concatenated to the label, to create a "dynamic" symbol name. 

symbol,ARG1[,ARG2,...]

	String literals can be specified with quotes around the string
	text.  Expression operators can also be used, but due to label
	parsing constraints, they should not contain spacing.

	The concat-eval "," operator also works on the expression side
	of EQU/SET pseudo-ops, so dynamic labels can be used with opcodes. 

WHY codes:
    Each bit in the WHY word (verbose option 1) is a reason (why
    the assembler needs to do another pass), as follows:

    bit 0   expression in mnemonic not resolved
	1   -
	2   expression in a DC not resolved
	3   expression in a DV not resolved (probably in DV's EQM symbol)
	4   expression in a DV not resolved (could be in DV's EQM symbol)
	5   expression in a DS not resolved
	6   expression in an ALIGN not resolved
	7   ALIGN: Relocatable origin not known (if in RORG at the time)
	8   ALIGN: Normal origin not known	(if in ORG at the time)
	9   EQU:   expression not resolved
	10  EQU:   value mismatch from previous pass (phase error)
	11  IF:     expression not resolved
	12  REPEAT: expression not resolved

	13  a program label has been defined after it has been
	    referenced (forward reference) and thus we need another
	    pass
	14  a program label's value is different from that of the
	    previous pass (phase error)

    Certain errors will cause the assembly to abort immediately, others
    will wait until the current pass is other.	The remaining allow another
    pass to occur in the hopes the error will fix itself.


HISTORIC VERSIONS: (pre github)

    V2.12
	-Fixed macro naming bug (macros wouldn't work if the name after
	 the 'mac' was in upper case).

    V2.11
	-Fixed <exp >exp bug, <exp now means LSB, >exp MSB (it used to
	 be reversed).
	-Fixed many bugs in macros and other things
	-Added automatic checksumming ... no more doing checksums manually!
	-Added several new processors, including 6502.
	-Source is now 16/32 bit int compatible, and will compile on an
	 IBM-PC (the ultimate portability test)

    V2.01

	-can now have REPEAT/REPEND's within macros
	-fill field for DS.W is a word (used to be a byte fill)
	-fill field for DS.L is a long (used to be a byte fill)

