Motorola M68CPU32BUG Manuel d'utilisateur télécharger pdf (Page 40)

OPERATING INSTRUCTIONS

M68332BCC/D 3-12 MOTOROLA

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3.5 ASSEMBLING/DISASSEMBLING PROCEDURE

The assembler/disassembler is an interactive, one-line assembler/editor in which the source

program is not saved. Each source line is converted into machine language code and is stored in

memory on a line-by-line basis at the time of entry. In order to display an instruction, the

machine code is disassembled and the instruction mnemonic and operands are displayed. All

valid opcodes are converted to assembly language mnemonic. All invalid opcodes return a

Declare Constant Word (DC.W) conversion.

The memory modify (mm ;di) command lets the user create, modify, and debug MC68332 MCU

code. Assembler input must have exactly one space between the mnemonic and the operand.

There must be no space inside the operand field. Assembler input must be terminated by a

carriage return. No comments are allowed after the instruction input and no line labels are

permitted.

After each new assembler input line, the new line is disassembled for the user before stepping to

the new instruction. The new line may assemble to a different number of bytes than the previous

one.

For Branch if Higher or Same (BHS)/Branch if Carry Clear (BCC) mnemonics, disassembly

displays the BCC mnemonic. For Branch if Lower (BLO)/Branch if Carry Set (BCS)

mnemonics, disassembly displays the BCS mnemonic.

Branch address offsets are automatically calculated by the assembler, so the user should input the

destination address rather than an offset value.

The assembler is terminated by entering a period (.) followed by a carriage return as the only

entry on the command input line. Entering a carriage return alone on an input line steps to the

next instruction.

The following pages describe how to operate the assembler/disassembler by creating a typical

program loop, and debugging the program using CPU32Bug monitor commands. A typical

program loop is first assembled. Routine examples then illustrate how to set a breakpoint,

proceed from a breakpoint, display and modify registers, and initiate user program execution.

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Motorola M68CPU32BUG Manuel d'utilisateur Page 40