Memory Requirements; Ppcbug Implementation; Mpu, Hardware, And Firmware Initialization - Motorola MCP750HA Series Installation And Use Manual

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.

Memory Requirements

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

MPU, Hardware, and Firmware Initialization

The debugger performs the MPU, hardware, and firmware initialization
process. This process occurs each time the MCP750HA is reset or powered
up. The steps below represent high-level outline (not all of the detailed
steps are listed):
1. Sets MPU.MSR to known value.
2. Invalidates the MPU's data/instruction caches.
3. Clears all segment registers of the MPU.
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MPU, Hardware, and Firmware Initialization
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