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32-2
How to make ROM
Programmer’s Manual
32.1.1.1 ROM_RESET
This is used to map the 68K first 256 locations. In the boot strap code, it is defined
as:
SECTION
DC.L
DC.L
DCB.L
rom_reset
MON_STACKTOP
rom_start-ROMADDR
254,0
; section declaration
; stack address for boot code
; absolute address of boot code
; interrupt vector space
The labels MON_STACKTOP and rom_start declared in this region are resolved
with their absolute address only during link time. This implementation makes the
values for these locations dynamic and system integration can be independent to
the absolute location and size of the hardware system.
ROMADDR is declared in the Linker Specification File.
32.1.1.2 ROM_CODE
This regions is declared to store the boot strap code. Because this code is NOT
part of PPSM library, they are declared and executed in the beginning of the
memory map to avoid memory conflict.
The first line of this region MUST declare the label rom_start. This is required by
the region rom_reset to work out the PC start address.
The last line of this region should be a " jmp START" instruction. This is used to
start PPSM start-up code. The label START is pre-defined as the start location for
the startup code.
Figure 30-1 Memory map for boot strap code
0x000
0x008
PC/Stack
Vectors
0x400
0x1000
Boot Strap Code
PPSM Application Tasks
rom_reset
rom_code
Personal Portable System Manager
Programmer’s Manual
Part IV
System
Integrator’s
Guide
F
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