Personal Computer User Manual

Using PPCBug

http://www.motorola.com/computer/literature 3-3

Implementation and Memory Requirements

PPCBug is written largely in the C programming language, providing

benefits of portability and maintainability. Where necessary, assembly

language has been used in the form of separately compiled program

modules containing only assembler code.

Physically, PPCBug is contained in two socketed 32-pin PLCC Flash

devices that together provide 1MB of storage. The executable code is

checksummed at every power-on or reset firmware entry. The result

(which includes a precalculated checksum contained in the flash devices),

is verified against the expected checksum.

PPCBug requires a maximum of 768KB of read/write memory. The

debugger allocates this space from the top of memory. For example, a

system containing 64MB (0x04000000) of read/write memory will place

the PPCBug memory locations 0x03F40000 to 0x3FFFFFF. Additionally,

the first 1MB of DRAM is reserved for the exception vector table and

stack.

Using PPCBug

PPCBug is command-driven; it performs its various operations in response

to commands that you enter at the keyboard. When the

PPC6-Bug> prompt

appears on the screen, the debugger is ready to accept debugger

commands. When the

PPC6-Diag> prompt appears on the screen, the

debugger is ready to accept diagnostics commands. To switch from one

mode to the other, enter SD.

What you enter is stored in an internal buffer. Execution begins only after

you press the Return or Enter key. This allows you to correct entry errors,

if necessary, with the control characters described in the PPCBug

Firmware Package User’s Manual, listed in Appendix C, Related

Documentation.

After the debugger executes the command, the prompt reappears.

However, depending on what the user program does, if the command

causes execution of a user target code (that is, GO), then control may or

may not return to the debugger.