Motorola MVME2401-1, Installation And Use Manual

Page: 93 / 178

MPU, Hardware, and Firmware Initialization
http://www.mcg.mot.com/literature 5-3
5
Memory Requirements
PPCBug requires a maximum of 768KB of read/write memory (i.e.,
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 $03F40000 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 MVME240x is reset or powered
up. The steps below are a 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.
4. Clears all block address translation registers of the MPU.
5. Initializes the MPU-bus-to-PCI-bus bridge device.
6. Initializes the PCI-bus-to-ISA-bus bridge device.