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4.2.1
Source Line Format
Each source statement is a combination of operation and, as required, operand fields. Line
numbers, labels and comments are not used.
4.2.1.1 Operation Field
Since there is no label field, the operation field may begin in the first available column. It may
also follow one or more spaces. Entries can consist of one of three categories:
Operation codes which correspond to the M68300 Family instruction set.
Define constant directive (DC.W) defines a constant in a word location.
System call directive (SYSCALL) calls CPU32Bug system utilities.
The size of the data field affected by an instruction is determined by the data size codes. Some
instructions and directives can operate on more than one data size. For these operations, the data
size code must be specified or a default size applicable to the instruction is used. The size code
need not be specified if only one data size is permitted by an operation. The operation field is
followed by a period (.) and the data size code. The data size codes are:
B = Byte (8-bit data)
W = Word (16-bit data; the usual default size)
L = Longword (32-bit data)
When the instruction or directive does not have a data size attribute, the data size code is not
permitted.
EXAMPLES
LEA
(A0),A1
ADD.B
(A0),D0
ADD
D1,D2
ADD.L
A3,D3
EXAMPLE
SUBA.B
#5,A1
M68CPU32BUG/D
Legal
Load the effective address of the first operand into A1. The longword
size is the default (.B, .W not allowed) for this instruction.
Add the byte pointed to in A0 to the lowest order byte in D0.
Add the low order word of D1 to the low order word of D2. W is the
default size code for ADD.
Add the entire 32-bit (longword) contents of A3 to D3.
Illegal
Illegal size specification (.B not allowed in instruction SUBA). This
instruction would have subtracted the value 5 from the low order byte
of A1; byte operations on address registers are not allowed.
4-3
ASSEMBLER/DISASSEMBLER
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