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Programmer’s Manual
Personal Portable System Manager
Programmer’s Manual
How to make ROM
32-1
Chapter 32 How to make ROM
To make PPSM applications into ROM code, two items are needed which are
different from running PPSM applications using RAM memory version. These two
items are:
Boot Strap code
Linker Specification File for ROM
This chapter gives some description of how to make a ROM code version of
PPSM applications.
32.1
Boot Strap Code (boot.s)
The boot strap code performs the following functions:
Starts the 68K core upon reset
Map the chip-selects of MC68328 to run on a particular hardware
platform
Initialization of peripheral devices on the MC68328
Jump into PPSM start-up code
Depending on the size and address of ROM that are used, the chip selects inside
boot.s need to be changed accordingly.
32.1.1
68K Start-up
In 68K architecture, the first 256 locations in the memory address space, 0x0 to
0x400, are reserved for system vector usage and cannot be over-written with
random values. The first two 32-bit words locations (address 0x00 and 0x04) are
defined for the start program counter address and the stack address upon power
reset.
In order to make this assignment of addresses re-locatable at link time, rather
than hard-coding the addresses at compilation time, two new regions, rom_reset
and rom_code, are defined by PPSM in the linker specification file to perform the
mapping.
F
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