SH7672 datasheet(131/1292 Pages) RENESAS

131 / 1292 page

Section 4 Cache

Rev. 1.00 Nov. 14, 2007 Page 105 of 1262

REJ09B0437-0100

4.4.3

Usage Examples

(1)

Invalidating Specific Entries

Specific cache entries can be invalidated by writing 0 to the entry's V bit in the memory mapping

cache access. When the A bit is 1, the tag address specified by the write data is compared to the

tag address within the cache selected by the entry address, and data is written to the bits V and U

specified by the write data when a match is found. If no match is found, there is no operation.

When the V bit of an entry in the address array is set to 0, the entry is written back if the entry's U

bit is 1.

An example when a write data is specified in R0 and an address is specified in R1 is shown below.

; R0=H'0110 0010; tag address(28-11)=B'0 0001 0001 0000 0000 0, U=0, V=0

; R1=H'F080 0088; operand cache address array access, entry=B'000 1000, A=1

;

MOV.L

R0,@R1

(2)

Reading the Data of a Specific Entry

The data section of a specific cache entry can be read by the memory mapping cache access. The

longword indicated in the data field of the data array in figure 4.4 is read into the register.

An example when an address is specified in R0 and data is read in R1 is shown below.

; R0=H'F100 004C; instruction cache data array access, entry=B'000 0100,

; Way=0, longword address=3

;

MOV.L

@R0,R1

4.4.4

Notes

1. Programs that access memory-mapped cache should be placed in a cache-disabled space.

2. Rewriting the address array contents so that two or more ways are hit simultaneously is

prohibited. Operation is not guaranteed if the address array contents are changed so that two or

more ways are hit simultaneously.

3. Memory-mapped cache can be accessed only by the CPU and not by the DMAC. Registers can

be accessed by the CPU and the DMAC.

SH7672 Datasheet(PDF) 131 Page - Renesas Technology Corp