Freescale Semiconductor MPC5565, Справочное руководство

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Flash Memory
MPC5565 Microcontroller Reference Manual, Rev. 1.0
13-20 Freescale Semiconductor
28–30
PFLIM
Prefetch limit. Controls the prefetch algorithm used by the FBIU prefetch controller. This field defines a limit
on the maximum number of sequential prefetches which are attempted between buffer misses. This field is
cleared by hardware reset.
000 No prefetching is performed
001 A single additional line (next sequential) is prefetched on a buffer miss
010 Up to two additional lines can be prefetched following each buffer miss before prefetching is halted. A
single additional line (next sequential) is prefetched on a buffer miss, and the next sequential line is
prefetched on a buffer hit (if not already present).
011 Up to three additional lines can be prefetched following each buffer miss before prefetching is halted.
Only a single additional prefetch is initiated after each buffer hit or miss.
100 Up to four additional lines can be prefetched following each buffer miss before prefetching is halted.
Only a single additional prefetch is initiated after each buffer hit or miss.
101 Up to five additional lines can be prefetched following each buffer miss before prefetching is halted. Only
a single additional prefetch is initiated after each buffer hit or miss.
110 An unlimited number of additional lines can be prefetched following each buffer miss. Only a single
additional prefetch is initiated on each buffer hit or miss.
111 Reserved
31
BFEN
FBIU line read buffers enable. Enables or disables line read buffer hits. It is also used to invalidate the buffers.
These bits are 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 can be set when the
buffers are successfully filled.
Note: Disable prefetching before invalidating the buffers. This includes starting a program or erase operation,
or turning on and off the buffers.
1
APC, WWSC, and RWSC values are determined by the maximum frequency of operation. Refer to Table 13-14 .
Table 13-14. FLASH_BIU Settings vs. Frequency of Operation
Maximum Frequency (MHz) APC RWSC WWSC DPFEN IPFEN PFLIM BFEN
up to and including 82 MHz
1
1
This setting allows for 80 MHz system clock with 2% frequency modulation.
0b001 0b001 0b01 0b00,
0b01, or
0b11
2
2
For maximum flash performance, set to 0b11.
0b00,
0b01, or
0b11
2
0b000-
0b110
3
3
For maximum flash performance, set to 0b110.
0b0, 0b1
4
4
For maximum flash performance, set to 0b1.
up to and including 102 MHz
5
5
This setting allows for 100 MHz system clock with 2% frequency modulation.
0b001 0b010 0b01 0b00,
0b01, or
0b11
2
0b00,
0b01, or
0b11
2
0b000-
0b110
3
0b0, 0b1
4
up to and including132 MHz
6
6
This setting allows for 130 MHz system clock with 2% frequency modulation.
0b010 0b011 0b01 0b00,
0b01, or
0b11
2
0b00,
0b01, or
0b11
2
0b000-
0b110
3
0b0, 0b1
4
Default Setting after Reset 0b111 0b111 0b11 0b00 0b00 0b000 0b0
Table 13-13. FLASH_BIUCR Field Descriptions (continued)
Bits Description