CRASM

Cross assembler for 6800/6801/6803/6502/65C02/Z80.

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SYNOPSIS

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.

 

OPTIONS

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

 

SYNTAX

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

[;comment]
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

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.

 

Constants

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

TypeFormatExamples
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.
0Bdddd0b1100
ascii'cccc''a', 'AB', '"', '\n', '\''.
"cccc""a", "AB", "'", "\n", "\"".

 

Expressions

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.

SyntaxResultDescription
abs{abs}bspecbit reference, e.g. pia{3}
ADDR(abs)absaddress from a bit reference
BIT(abs)absbit number from a bit reference
absabstwo's complement
absabsone's complement
abs << absabsleft shift
abs >> absabsright shift
abs | absabsbitwise or
abs & absabsbitwise and
abs ^ absabsbitwise xor
abs * absabsmultiplication
abs * absabsdivision
abs + absabsaddition
rel + absreladdition
abs - absabssubtraction
rel - absrelsubtraction
rel - relrelsubtraction
reg - regreglistregister range
reglist \ regreglistregister list construction

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.

Examples:

(base+$12) >> 8 & 0xff00
'A'-80H
(base+0x12)

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.

 

Pseudo-mnemonics

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.

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

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

MLIST ON
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.

 

EXAMPLE

Here is a small 6502 program:

              cpu 6502
          cout = $fded ; display a character
             * = $300  ; assemble at $300
               code
          pstring  ldy #0
          .1       lda message,y
                   beq .2
                   jsr cout
                   iny
          .2       bne .1
                   rts
          message  asc "This is the message "
               code

Assembling this program gives the following listing:

Crasm LYB 1.3:                                                   page  1

                         1
                         2              cpu 6502
  FDED                   3            cout = $fded ; display a character
  0300                   4               * = $300  ; assemble at $300
                         5                 code
0300 A000                6            pstring  ldy #0
0302 B90E03              7            .1       lda message,y
0305 F004                8                     beq .2
0307 20EDFD              9                     jsr cout
030A C8                 10                     iny
030B D0F5               11            .2       bne .1
030D 60                 12                     rts
030E 54686973206973
0315 20746865206D65
031C 737361676500       13            message  asc "This is the message\0"
                        14                 code
                        15

ERRORS:       0
WARNINGS:     0

Successful assembly...
 Last address      321 (801)
 Code length        44 (68)



Crasm LYB 1.3:                                                   page  2

 FDED   Abs COUT
^030E   Abs MESSAGE
?0300   Abs PSTRING
and the following S Code file:
S1130300A000B90E03E00420EDFDC8D0F5605468E8
S1130310697320697320746865206D657373616700
S1050320650072
S9030000FC
 

CREDITS

Leon Bottou, September 1987.


 

Index

SYNOPSIS
OPTIONS
SYNTAX
Labels
Constants
Expressions
Pseudo-mnemonics
EXAMPLE
CREDITS