Motorola MVME2700 Series Servisní příručka stáhnout pdf (Strana 156)

5-2 Computer Group Literature Center Web Site

PPCBug Firmware

Because PPCBug is command-driven, it performs its various operations in

response to user commands entered at the keyboard. When you enter a

command, PPCBug executes the command and the prompt reappears.

However, if you enter a command that causes execution of user target code

(for instance, GO), then control may or may not return to PPCBug,

depending on the outcome of the user program. The flow of control in

PPCBug is described in the PPCBug Firmware Package User’s Manual,

listed in Appendix D, Related Documentation.

PPCBug is similar to previous Motorola firmware debugging packages

(MVME147Bug, MVME167Bug, MVME187Bug), with differences due

to microprocessor architectures. These are primarily reflected in the

instruction mnemonics, register displays, addressing modes of the

assembler/disassembler, and the passing of arguments to the system calls.

Memory Requirements

PPCBug requires a total of 768KB of read/write memory (for example,

DRAM). The debugger allocates this space from the top of memory. For

example, a system containing 64MB ($04000000) of read/write memory

will place the PPCBug memory page at locations $03F80000 to

$03FFFFFF.

Implementation

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. No mixed-language modules are

used.

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, and the result

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

is verified against the expected checksum.

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Motorola MVME2700 Series Servisní příručka Strana 156