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Chapter 10: Using Memory Management
Understanding Emulation and Analysis Of The Memory Management Unit
What are logical addresses?
Logical addresses are the addresses that are assigned to your program code when
you develop your program. They are the addresses represented by symbols in your
symbols data base (the symbol "Main" represents a logical address).
What are physical addresses?
Physical addresses are the addresses assigned by the MMU to contain your
program. Physical addresses identify locations where you actually have memory
hardware in your target system. Physical addresses appear on the processor address
bus instead of logical addresses.
Static and dynamic system architectures
There are several design strategies where memory management can help in
developing a system or product. Three of these are described in the following
paragraphs. One shows memory management used in a static memory system. The
other two show memory management used in different dynamic memory systems.
The MC68040 emulator is designed to work in any of these system types; however,
the deMMUer which provides reverse translations to the analyzer is primarily
intended for use in static systems.
Static system example
A static system design may use the MMU simply to protect supervisor code and I/O
space against accesses from a user program. Once a static system is initialized, it
never changes. Your HP emulator and analyzer can give you complete support for
a static memory management system. After the MMU has been set up to manage
memory in a static system, the deMMUer can be loaded with information to reverse
the MMU translations over the entire range managed by the MMU.
Non-paged dynamic system example
Assume three programmers are developing separate programs to run in a real-time
operating system environment. The programmers each write their programs to
begin at address 0h. The operating system accepts the responsibility to know where
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