Reserved Memory Spaces - Motorola DSP56367 User Manual

Memory Configuration
Data and Program Memory Maps
5.1.1

RESERVED MEMORY SPACES

The reserved memory spaces should not be accessed by the user. They are reserved for future
expansion.
5.1.2 PROGRAM ROM AREA RESERVED FOR MOTOROLA USE
The last 128 words ($FFAF80-$FFAFFF) of the Program ROM are reserved for Motorola
use. This memory area is reserved for use as expansion area for the bootstrap ROM as well as
for testing purposes. Customer code should not use this area. The contents of this Program
ROM segment is defined by the Bootstrap ROM Contents on page Appendix A-1.
5.1.3 BOOTSTRAP ROM
The 192-word Bootstrap ROM occupies locations $FF0000-$FF00BF. The bootstrap ROM is
factory-programmed to perform the bootstrap operation following hardware reset. The
contents of the Bootstrap ROM are defined by the Bootstrap ROM source code in Bootstrap
ROM Contents on page Appendix A-1.
5.1.4 DYNAMIC MEMORY CONFIGURATION SWITCHING
The internal memory configuration is altered by re-mapping RAM modules from Y and X
data memory into program memory space and vice-versa. The contents of the switched RAM
modules are preserved.
The memory can be dynamically switched from one configuration to another by changing the
MS, MSW0 or MSW1 bits in OMR. The address ranges that are directly affected by the
switch operation are specified in Table 5-2. The memory switch can be accomplished
provided that the affected address ranges are not being accessed during the instruction cycle in
which the switch operation takes place. Accordingly, the following condition must be
observed for trouble-free dynamic switching:
Note: No accesses (including instruction fetches) to or from the affected address ranges
in program and data memories are allowed during the switch cycle.
Note: The switch cycle actually occurs 3 instruction cycles after the instruction that
modifies the MS, MSW0 or MSW1 bits.
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