HP 64783A, Руководство пользователя

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How the MMU affects the way you compose your
emulation commands
When you display registers, the address registers, stack pointers, and program
counter always contain logical addresses, even when the MMU is turned on.
If you place an address in the entry buffer and choose Execution
→
Run
→
from(),
or enter a run from <address> command, the address you enter must be a logical
address. The program counter will accept it and supply it to the MMU for
translation before it places the address on the processor bus.
Breakpoint addresses in RAM space are always logical addresses. When you set a
breakpoint at an address, that address is translated by the MMU and the BKPT
instruction replaces the instruction at the appropriate physical address. When the
breakpoint is executed, the emulator restores the original instruction to the physical
address, by first translating the logical address through the MMU.
Consider what happens if you set a breakpoint at a particular address, and before
the breakpoint is hit, you update the translation tables in the MMU, changing the
mapping to the location where the breakpoint is set. This is discussed in detail
under "Solving Problems" at the end of this chapter.
If you enter a command to display memory or modify memory, your command is
directed to logical address space. If you want to display memory at a physical
address, you have to change your command. For example, the command to display
memory at address 100H (Display
→
Memory
→
Hex(), or display memory 100h)
will show you the memory content at logical address 100H (which might be some
other physical address). If you want to see the content at physical memory address
100H, you will have to enter the command display memory physical 100h.
Addresses expressed using symbols are always logical addresses. In the case of
symbols, the emulator looks in the symbol data base and finds the logical address
that corresponds to the symbol you used in your command, and it loads that logical
address into the program counter.
If you attempt to modify a memory location that is write-protected by the MMU,
the emulator will temporarily modify the translation tables to allow access.
Chapter 10: Using Memory Management
Understanding Emulation and Analysis Of The Memory Management Unit
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