SH7763 Datasheet, PDF (267/2026 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC Engine Family SH-4A Series

Section 7 Caches
7.3.4 Write-Back Buffer
In order to give priority to data reads to the cache and improve performance, this LSI has a write-
back buffer which holds the relevant cache entry when it becomes necessary to purge a dirty cache
entry into external memory as the result of a cache miss. The write-back buffer contains one cache
line of data and the physical address of the purge destination.
Physical address bits [28:5] LW0 LW1 LW2 LW3 LW4 LW5 LW6 LW7
Figure 7.3 Configuration of Write-Back Buffer
7.3.5 Write-Through Buffer
This LSI has a 64-bit buffer for holding write data when writing data in write-through mode or
writing to a non-cacheable area. This allows the CPU to proceed to the next operation as soon as
the write to the write-through buffer is completed, without waiting for completion of the write to
external memory.
Physical address bits [28:0] LW0 LW1
Figure 7.4 Configuration of Write-Through Buffer
7.3.6 OC Two-Way Mode
When the OC2W bit in RAMCR is set to 1, OC two-way mode which only uses way 0 and way 1
in the OC is entered. Thus, power consumption can be reduced. In this mode, only way 0 and way
1 are used even if a memory-mapped OC access is made.
The OC2W bit should be modified by a program in the P2 area. At that time, if the valid line has
already been recorded in the OC, data should be written back by software, if necessary, 1 should
be written to the OCI bit in CCR, and all entries in the OC should be invalid before modifying the
OC2W bit.
Rev. 1.00 Oct. 01, 2007 Page 201 of 1956
REJ09B0256-0100