Motorola MVME2600 manual Memory Requirements, PPCBug Implementation

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PPCBug

Because PPCBug is command-driven, it performs its various operations in response to user commands entered at the keyboard. The flow of control in PPCBug is described in the PPCBug Firmware Package User’s Manual, listed in Appendix D, Related Documentation. 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 example, GO), then control may or may not return to PPCBug, depending on the outcome of the user program.

The PPCBug is similar to previous Motorola firmware debugging packages (for example, 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 maximum of 768KB (maybe less) of read/write memory (that is, 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.

PPCBug 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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