HP 64783A, User Manual

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The MMU Demonstration
The remainder of this demonstration shows how the MC68040 emulator helps you
develop and analyze your target program within a memory system that is managed
by the MMU of the MC68040 processor.
The MMU demo program attempts to simulate a real target system to display
hexadecimal characters on the seven-segment display on the HP 64783A demo
board (used with HP 64783A and HP 64783B emulators). A simple operating
system uses interrupts to maintain a system clock and configures the MMU to
translate addresses and provide memory access protection. The operating system
waits for a hexadecimal string to be placed in "sysbuf" and then spawns a user task
to display each character on the demo board’s seven-segment display. The user
task interfaces with the operating system to set up an alarm timer and to output
individual characters to the display. The display of characters is interrupt driven.
This demo requires 128 Kbytes of emulation memory. The first 64-Kbyte block of
emulation memory is mapped to lower memory and corresponds to system ROM.
ROM space is translated 1:1 and is entirely write protected. The first half of ROM
contains privileged operating system code and is also protected against user mode
access. The second half of ROM is user accessible and contains shared library and
operating system interface functions. The second 64-Kbyte block of emulation
memory is mapped to upper memory and corresponds to system RAM. RAM
space is NOT translated 1:1 and has varying access protections. During bootup, the
operating system loads the user program, user data, and operating system data from
ROM into RAM after the MMU is enabled. The user program is loaded into the
first half of RAM and gets write-protected. The user data and stack is located in the
next quarter of RAM and has no access protections. The last quarter of RAM
contains operating system data and stack and is protected against user access. A
transparent translation register is used to provide a 1:1 address translation for the
emulation monitor located at 0xff000000. The following MMU translation display
summarizes all address translations:
Logical Address Physical Address Attributes
00000000..00007fff 00000000..00007fff@a S W (32K sprog)
00008000..0000ffff 00008000..0000ffff@a W (32K libc)
00010000..00017fff ffff0000..ffff7fff@a W (32K uprog)
00010000..0001bfff ffff8000..ffffBfff@a (16K udata)
0001C000..0001ffff ffffC000..ffffffff@a S (16K sdata)
ff000000..ffffffff ff000000..ffffffff@a TT (monitor)
Where:
S = Supervisor access only.
W = Write-protected.
TT = Controlled by a transparent translation register.
Chapter 1: Getting Started
Step 12: Patch assembly language code
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