HD6417615 Hitachi Semiconductor, HD6417615 Datasheet - Page 371

• Manufacturer Part Number: HD6417615
• Description: Hardware Manual
• Manufacturer: Hitachi Semiconductor

Bit 5—Write-Back Bit (WB): Specifies the cache operation method when the cache area is
accessed.
Bit 5: WB
0
1
Bit 4—Cache Purge Bit (CP): When 1 is written to the CP bit, all cache entries and the valid bits,
and LRU information of all ways are initialized to 0. After initialization is completed, the CP bit
reverts to 0. The CP bit always reads 0.
Bit 4: CP
0
1
Note: Always read 0.
Bit 3—Two-Way Mode (TW): TW is the two-way mode bit. The cache operates as a four-way set
associative cache when TW is 0 and as a two-way set associative cache and 2-kbyte RAM when
TW is 1. In the two-way mode, ways 2 and 3 are cache and ways 0 and 1 are RAM. Ways 0 and 1
are read or written by direct access of the data array according to address space specification.
Bit 3: TW
0
1
Bit 2—Data Replacement Disable Bit (OD): OD is the bit for disabling data replacement. When
this bit is 1, data fetched from external memory is not written to the cache even if there is a cache
miss. Cache data is, however, read or updated during cache hits. OD is valid only when CE is 1.
Bit 2: OD
0
1
Description
Write-through
Write-back
Description
Normal operation
Cache purge
Description
Four-way mode
Two-way mode
Description
Normal operation
Data not replaced even when cache miss occurs in data access
(Initial value)
(Initial value)
(Initial value)
(Initial value)
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