Use The Analyzer With The Demmuer To Find Mmu Mapping Problems; Failure Caused By Access To Guarded Memory - HP MC68040 User Manual

Chapter 10: Using Memory Management
Solving Problems
emulator will let you specify correct values to be used when composing the display
of translations You can use the dialog box that is called by the Display→MMU
Translations... selection and click on Override Processor Register Values and enter
the desired values for the TC, SRP, URP, ITT0, ITT1, DTT0, and DTT1 registers
(or RECALL desired values from earlier usages). If you are using the command
line, you can use the use_value option to the display mmu_translations
command and specify any of the above registers with desired values to obtain the
display of MMU translations.
Use the analyzer with the deMMUer to find MMU
mapping problems
If your system operates properly until you turn on the MMU, and then it fails, the
problem is most likely in the mappings used by the MMU to translate logical
addresses to physical addresses. You could go down the list of logical-to-physical
translations to see the mapping scheme used to translate each logical address to its
corresponding physical address, but normally that would take too much time. The
analyzer can help you identify the one, or few, logical addresses that are being
mapped incorrectly by the MMU. Then you can choose Display→MMU
Translations..., click on MMU Tables in the dialog box, and enter the suspect
addresses to see the mapping tables used to translate those addresses. On the
command line, you can use the display mmu_translations tables <address>
command to look at the mapping tables used to translate the suspected addresses.

Failure caused by access to guarded memory

If the problem is an access to guarded memory, remember that guarded memory is
guarded physical memory. You need to find the logical address that the MMU
improperly translated to guarded physical memory and then investigate the
mappings the MMU used to perform the translation.
Begin by looking at the registers display (Display→Registers→BASIC or display
registers) to see the value of the logical address in the program counter. Then
choose Display→MMU Translations..., and use the dialog box, or use the
display mmu_translations tables <address> command to see the path through the
tables that the MMU took when it translated that logical address to a guarded
address in physical memory. Note that the value of the program counter may have
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