User`s manual

Comparison with the Standard Assembler

4-2

Machine-Instruction Operation Codes

Refer to PowerPC 603 RISC Microprocessor UserÕs Manual, PowerPC

604 RISC Microprocessor UserÕs Manual, or the PowerPC MCP750

RISC Microprocessor UserÕs Manual for information on the

mnemonic machine instruction operation codes.

Directives

The PPCBug one-line assembler recognizes only two mnemonic

directives: to define a word constant (WORD), and system call

(SYSCALL). These directives are used to define data within the

program, and to make calls on PPCBug utilities. Refer to WORD

Define Constant Directive on page 4-9 and SYSCALL System Call

Directive on page 4-10 for further details.

Comparison with the Standard Assembler

There are several major differences between the PPCBug one-line

assembler and the PowerPC Standard Assembler. The PowerPC

assembler is a two-pass assembler that processes an entire program

as a unit, while the PPCBug one-line assembler processes each line

of a program as an individual unit. Because of this, the capabilities

of the PPCBug one-line assembler are more restricted, as described

below:

❏ Label and line numbers are not used. Labels are used to

reference other lines and locations in a program. The one-line

assembler has no knowledge of other lines and, therefore,

cannot make the required association between a label and the

label definition located on a separate line.

❏ Source lines are not saved. In order to read back a program

after it has been entered, the machine code is disassembled

and then displayed as mnemonic and operands.

❏ Only two directives (WORD and SYSCALL) are accepted.

❏ No macro operation capability is included.