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Firmware
When using PPCBug, you operate out of either the debugger directory or the diagnostic
directory.
If you are in the debugger directory, the debugger prompt PPC-Bug> is displayed and you
have all of the debugger commands at your disposal
If you are in the diagnostic directory, the diagnostic prompt PPC-Diag> is displayed and you
have all of the diagnostic commands at your disposal as well as all of the debugger
commands
Use the SD command to go back and forth between these directories.
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 example, GO), then control may or may not return to PPCBug,
depending on the outcome of the user program.
5.3
Memory Requirements
PPCBug requires a minimum of 1 MB of read/write memory (that is, DRAM for its own data
storage purposes). The debugger allocates this space from the top of memory. The amount of
memory that PPCBug is allowed to allocate for it's own use is controlled by an NVRAM tunable
value. For example, a system containing 64 MB ($04000000) of read/write memory, using 1 MB
of memory, will place the PPCBug memory page at locations $03F00000 to $03FFFFFF. In
addition, PPCBug will use certain parts of low memory (typically from $0 to $4000) for exception
vector table data. Avoid using any predefined address space in order to alleviate writing over
any existing firmware code or data.
5.4
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 1 MB 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.
5.5
MPU, Hardware and Firmware Initialization
The debugger performs the MPU, hardware and firmware initialization process. This process
occurs each time the CPCI-6020 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 a known value.
2. Invalidates the MPU's data/instruction caches.
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CPCI-6020 CompactPCI Single Board Computer Installation and Use (6806800A51C)
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Memory Requirements
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