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Flash memory
MPC5644A Microcontroller Reference Manual, Rev. 6
236
Freescale Semiconductor
RWSC
Read Wait State Control
This field is used to control the number of wait-states to be added to the best-case flash array access
time for reads. The best-case flash array access time for reads is one cycle. This field must be set to
a value corresponding to the operating frequency of the PFLASH and the actual read access time of
the PFLASH
. Higher operating frequencies require non-zero settings for this field for proper flash
operation.
This field is set to 0b111 by hardware reset.
000: No additional wait-states are added
001: One additional wait-state is added
...
111: Seven additional wait-states are added
Note:
The settings for APC and RWSC should be the same.
DPFEN
Data Prefetch Enable
This field enables or disables prefetching initiated by a data read access. This field is cleared by
hardware reset.
0: No prefetching is triggered by a data read access
1: Prefetching may be triggered by any data read access
IPFEN
Instruction Prefetch Enable
This bit enables or disables prefetching initiated by an instruction read access. This field is cleared by
hardware reset.
0: No prefetching is triggered by an instruction read access
1: Prefetching may be triggered by any instruction read access
PFLIM
PFLASH Prefetch Limit
This field controls the prefetch algorithm used by the PFLASH prefetch controller. This field defines a
limit on the maximum number of sequential prefetches which will be attempted between buffer misses.
In all situations when enabled, only a single prefetch is initiated on each buffer miss or hit. This field is
cleared by hardware reset.
00: No prefetching or buffering is performed.
01: The referenced line is prefetched on a buffer miss, that is, prefetch on miss.
1x: The referenced line is prefetched on a buffer miss, or the next sequential line is prefetched on a
buffer hit (if not already present), that is, prefetch on miss or hit.
BFEN
PFLASH Line Read Buffers Enable
This bit enables or disables line read buffer hits. It is also used to invalidate the buffers. This bit is
cleared by hardware reset.
0: The line read buffers are disabled from satisfying read requests, and all buffer valid bits are cleared.
1: The line read buffers are enabled to satisfy read requests on hits. Buffer valid bits may be set when
the buffers are successfully filled.
1
Valid settings are specified in the device data sheet.
Table 12-12. BIUCR field descriptions (continued)
Field
Description
Summary of Contents for MPC5644A
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