HP 64783A, User Manual

Page: 210 / 816

Using The Emulator With MMU Enabled
When you enable memory management in the MC68040 emulator, many
capabilities and features become available that are not otherwise offered. Also,
some of the features of the emulator behave differently. The remaining pages in
this chapter will help you when you are using the MC68040 emulator with the
MMU enabled. Chapter 10, "Using Memory Management", provides detailed
information to help you use the MC68040 MMU most efficiently.
Disable the MMU unless you are using it for address translation. You will still be
able to use the transparent translation registers for such tasks as defining cache
modes.
To enable the processor memory management
unit
In order to use the MC68040 MMU to provide logical-to-physical address
translation, the MMU must be enabled within the emulator configuration and the
target system must deassert the MDIS signal (MMU Disable). If the MMU is not
enabled within the emulator configuration, the emulator asserts the MDIS signal
and ignores the MDIS signal from the target system, thus preventing the target
system from using the MMU. If you are using the background monitor, you will
need to select a foreground monitor before the MMU can be enabled within the
emulator configuration. Refer to the chapter titled "Configuring the Emulator" for
details of setting up the emulator configuration.
Once the MDIS signal is driven properly, the target system software is responsible
for setting up address translation tables in memory and initializing the processor’s
MMU registers at run time. This task is typically managed by the target system’s
boot code or operating system. Refer to your Motorola 68040 User’s Manual for
information on how to use the MMU.
If the emulator is being used in an MC68EC040 target system, or if the MMU is
not needed for translating page addresses from address translation tables in
memory, then you should disable the MMU within the emulator configuration.
This causes the emulator to assert the MDIS signal. However, the assertion of this
Chapter 4: Using the Emulator
Using The Emulator With MMU Enabled
180