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Section 8 Cache
Page 214 of 2108 R01UH0134EJ0400 Rev. 4.00
Sep 24, 2014
SH7262 Group, SH7264 Group
8.2.2 Cache Control Register 2 (CCR2)
CCR2 is used to enable or disable the cache locking function for operand cache and is valid in
cache locking mode only. In cache locking mode, the lock enable bit (the LE bit) in CCR2 is set to
1. In non-cache-locking mode, the cache locking function is invalid.
When a cache miss occurs in cache locking mode by executing the prefetch instruction (PREF
@Rn), the line of data pointed to by Rn is loaded into the cache according to bits 9 and 8 (the
W3LOAD and W3LOCK bits) and bits 1 and 0 (the W2LOAD and W2LOCK bits) in CCR2. The
relationship between the setting of each bit and a way, to be replaced when the prefetch instruction
is executed, are listed in table 8.3. On the other hand, when the prefetch instruction is executed
and a cache hit occurs, new data is not fetched and the entry which is already enabled is held. For
example, when the prefetch instruction is executed with W3LOAD = 1 and W3LOCK = 1
specified in cache locking mode while one-line data already exists in way 0 which is specified by
Rn, a cache hit occurs and data is not fetched to way 3.
In the cache access other than the prefetch instruction in cache locking mode, ways to be replaced
by bits W3LOCK and W2LOCK are restricted. The relationship between the setting of each bit in
CCR2 and ways to be replaced are listed in table 8.4.
Programs that change the contents of CCR2 should be placed in a cache-disabled space, and a
cache-enabled space should be accessed after reading the contents of CCR2.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
0
0000000000000000
RRRRRRRRRRRRRRRR/W
0000000000000000
R R R R R R R/W R/W R R R R R R R/W R/W
Bit:
Initial value:
R/W:
Bit:
Initial value:
R/W:
Note: The W3LOAD and W2LOAD bits should not be set to 1 at the same time.*
---------------LE
------
W3
LOAD*
W3
LOCK
W2
LOAD*
W2
LOCK
------