crasm(1) Cross assembler for 6800/6801/6803/6502/65C02/Z80


crasm [-o codefile] [-slx] asmfile

Assemble the microprocessor program asmfile and produce output file codefile in Intel HEX or Motorola S Code format. A program listing and a symbol table are also produced on the standard output. The current version of crasm can assemble programs for the 6800, 6801, 6803, 6502, 65C02, and Z80 processors. The full list is printed when you invoke crasm without arguments.


-o codefile
Specify the name of the output file. No output file is produced without this option.
Disable warnings.
Disable program listing output.
Disable symbol table output.


Each line of the assembly program should follow one of the following templates, where the brackets delimit optional parts.

label = expression [;comment]
[label] mnemonic operand [;comment]

Comments are introduced by a semicolon (;) and extend to the end of the line. Labels are identifiers containing up to 36 alphanumeric characters (including period and underscore). Labels cannot start with a digit. The format of the mnemonics and operands field depends on the selected micro-processor. A few mnemonics are valid for all processors and are used to give directives to the assembled. These are known as "pseudo-mnemonics".


Labels are identifiers representing
--- an absolute address,
--- a relative address (position independent code),
--- a register,
--- a list of registers,
--- a specific bit at a specific address,
--- or a mnemonic.

Most labels are composed of at most 36 alphanumeric characters, periods (.) or underscores (_). Labels cannot start with a digit. They are case insensitive.

Labels starting with a period (.) are local labels whose scope is either limited to the macro in which they are defined, or to the code segment delimited by the pseudo-mnemonics CODE or DUMMY.

The predefined "star" label (*) represents the current program counter, that is to say, the address where the next assembly code instruction will be encoded. Other predefined labels include all pseudo-mnemonics, micro-processor specific mnemonics and register names.


The assembled recognizes numerical constants expressed in decimal, hexadecimal, octal, binary, or ascii.


decimaldddd1234, 675, 12, 1, but not 0.12.

hexadecimal$dddd$fd12, $2AC, $0.
ddddH03H, 2da7H, 0FC84H, but not FC84H.
0Xdddd0x03, 0x2AC, 0Xfc84.

octalddddQ377Q, 012412Q.

binary%dddd%01110110, %1100.
ddddB01110110B, 1100B.

ascii'cccc''a', 'AB', '"', '\n', '\''.


Like labels, expressions can represent an absolute address (abs), a relative address for position independent code (rel), a register (reg), or a list of registers (reglist), or a reference to a specific bit at a specific address (bspec).

The following operators are recognized on expressions.


bspecbit reference, e.g. pia{3}

absaddress from a bit reference

absbit number from a bit reference

abstwo's complement

absone's complement

 abs << abs
absleft shift

 abs >> abs
absright shift

 abs | abs
absbitwise or

 abs & abs
absbitwise and

 abs ^ abs
absbitwise xor

 abs * abs

 abs * abs

 abs + abs

 rel + abs

 abs - abs

 rel - abs

 rel - rel

 reg - reg

 reglist \ reg

The table lists operators in order of decreasing precedence. Parenthesis can be used to avoid ambiguities. A warning is generated when an entire expression is surrounded with parenthesis and can be confused with a micro-processor addressing mode.


(base+$12) >> 8 & 0xff00

The last example causes a warning because the parenthesis were not necessary and might suggest a micro-processor addressing mode.

All arithmetic expressions are evaluated on 32 bits. Arithmetic operations overflow silently. The arithmetic values are then truncated to the size implied by the micro-processor mnemonic. This truncation might cause a warning message.

Examples: all the following instructions

(6502) lda #$1234

(6800) ldaa $1234,x

(Z80)  ld (ix+0C2H),b

cause a warning

>>> WARNING: Operand overflow

However expression

$1123454 * 1298992

overflows silently.


The following pseudo-mnemonics are always recognized.

CPU cpuname Indicates the selected micro-processor type. This must appear before anu micro-processor specific instruction. The possible values of cpuname are listed when you invoke crasm without arguments. The current list includes 6800, 6801, 6803, 6502, 65C02, and Z80

OUTPUT binformat Indicates the format of the output file. Argument binformat can take values SCODE for producing an output file using Motorola's S code, or HEX for Intel's Hex format. The default depends on the selected micro-processor.

CODE Delimit the scope of local labels and introduce a program section.

Delimit the scope of local labels and introduce a fake program section whose sole effect is to define labels without generating code.

label EQU expression
label = expression Define the value of label label. Labels defined using these directives can be redefined later in the program.

[label] DB expression[,...,expression] Insert the specified data bytes (8 bits).

[label] DW expression[,...,expression] Insert the specified data words (16 bits). The byte ordering depends on the selected micro-processor.

[label] DL expression[,...,expression] Insert the specified data longs (32 bits). The byte ordering depends on the selected micro-processor.

[label] DDB expression[,...,expression] Insert the specified double bytes (16 bits). The byte ordering is the opposite of the usual byte ordering for the selected micro-processor.

[label] ASC stringconstant Insert the ascii representation of the string stringconstant . The string must be delimited by double quotes. The C escape sequences \r, \n, \t, \0, \', \", and \\ are recognized.

[label] DS countexpr,[valexpr] Insere countexpr bytes with value valexpr. The default value is zero.

[label] ALIGN EVEN
[label] ALIGN ODD Insert a null byte in order to make the program counter even or odd.

IF condexpr


ENDC Conditional assembly: If expression condexpr is non zero, process the lines located between the IF and the ELSE pseudo-mnemonics. Otherwise process the lines located between the ELSE and the ENDC pseudo-mnemonics. Conditional assembly instructions can be nested. The ELSE part can be omitted.

label MACRO

Define a new mnemonic label equivalent to all the instructions located between the MACRO and ENDM pseudo-mnemonics. Invocations of the macro can specify a list of comma separated operands. The character sequences \1, \2, ... \N in the macro definition are replaced by the supplied operands. The character sequence \0 is replaced by the number of supplied operands.

EXITM This pseudo mnemonic can be used inside a macro definition to exit the macro. This is useful in conjunction with the conditional assembly pseudo-mnemonics.

INCLUDE filename Force the assembler to process file named filename at the current point.

LIST OFF Enable or disable the production of a listing (default is on.)

CLIST OFF Enable or disable the production of a listing for the non active branches of a conditional assembly construct (default is on.)

ILIST OFF Enable or disable the production of a listing for included files (default is off.)

MLIST OFF Enable or disable the production of a listing for the macro expansions (default is off.)

NAM title Provide name title for the header of the listing pages.

PAGE Start a new listing page.

PAGE columns,rows Specify the size of a listing page.

SKIP number Skip number lines.

FAIL message Generate an error message message.


Here is a small 6502 program:

     cpu 6502

 cout = $fded ; display a character

    * = $300  ; assemble at $300


 pstring  ldy #0

 .1       lda message,y

          beq .2

          jsr cout


 .2       bne .1


 message  asc "This is the message "



Leon Bottou, September 1987.