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User’s Manual
M68HC12A4EVB Evaluation Board — Rev. 1
32
Configuration and Setup
MOTOROLA
Configuration and Setup
2.6.4 Changing the Baud Rate
The EVB’s default baud rate for the RS-232C ports is 9600. This can be
changed in two ways:
•
For temporary changes, use the D-Bug12 BAUD command. This change
remains in effect only until the next reset or power-up, when the baud
rate returns to 9600.
•
For permanent changes, the D-Bug12 baud-rate initialization value
stored in EPROM must be modified. For instructions, refer to
Appendix D. D-Bug12 Customization Data
and
Appendix E.
Customizing the EPROMs
.
2.7 Using Fast External RAM
To replace the two factory-supplied SRAM chips with parts capable of
operation at the full 16-MHz external clock speed (8-MHz E-clock) with no
wait states, two operations are required:
1.
Replace the SRAM chips with suitably fast parts. See
2.7.1 Selecting
and Replacing the RAM Chips
.
2.
Reprogram the SRAM chip select, CSD, for zero-wait-state operation.
See
2.7.2 Reprogramming the RAM Chip Select
.
2.7.1 Selecting and Replacing the RAM Chips
The replacement 8-Kbyte x 8-bit SRAM devices should have a chip-select
access time of less than 60 nanoseconds. An example of a device that has been
used successfully is the Integrated Device Technologies part number
IDT7164L25P (8 Kbytes x 8 bits, 25 ns).
When installing the replacement SRAM devices, make sure that their pins align
with the rightmost ends of sockets U4 and U6A, as viewed in
Figure 1-1. EVB
Layout and Component Placement
.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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