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Section 8 Cache
R01UH0134EJ0400 Rev. 4.00 Page 211 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
(3) LRU
With the 4-way set associative system, up to four instructions or data with the same entry address
can be registered in the cache. When an entry is registered, LRU shows which of the four ways it
is recorded in. There are six LRU bits, controlled by hardware. A least-recently-used (LRU)
algorithm is used to select the way that has been least recently accessed.
Six LRU bits indicate the way to be replaced in case of a cache miss. The relationship between
LRU and way replacement is shown in table 8.1 when the cache lock function (only for operand
cache) is not used (concerning the case where the cache lock function is used, see section 8.2.2,
Cache Control Register 2 (CCR2)). If a bit pattern other than those listed in table 8.1 is set in the
LRU bits by software, the cache will not function correctly. When modifying the LRU bits by
software, set one of the patterns listed in table 8.1.
The LRU bits are initialized to B'000000 by a power-on reset but not initialized by a manual reset
or in software standby mode.
Table 8.1 LRU and Way Replacement (Cache Lock Function Not Used)
LRU (Bits 5 to 0) Way to be Replaced
000000, 000100, 010100, 100000, 110000, 110100 3
000001, 000011, 001011, 100001, 101001, 101011 2
000110, 000111, 001111, 010110, 011110, 011111 1
111000, 111001, 111011, 111100, 111110, 111111 0