HD6417750RF240DV Datasheet, PDF (171/1132 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family / SH7750 Series

SH7750, SH7750S, SH7750R Group
Section 4 Caches
• Tag
Stores the upper 19 bits of the 29-bit external memory address of the data line to be cached.
The tag is not initialized by a power-on or manual reset.
• V bit (validity bit)
Indicates that valid data is stored in the cache line. When this bit is 1, the cache line data is
valid. The V bit is initialized to 0 by a power-on reset, but retains its value in a manual reset.
• U bit (dirty bit)
The U bit is set to 1 if data is written to the cache line while the cache is being used in copy-
back mode. That is, the U bit indicates a mismatch between the data in the cache line and the
data in external memory. The U bit is never set to 1 while the cache is being used in write-
through mode, unless it is modified by accessing the memory-mapped cache (see section 4.5,
Memory-Mapped Cache Configuration (SH7750, SH7750S)). The U bit is initialized to 0 by a
power-on reset, but retains its value in a manual reset.
• Data field
The data field holds 32 bytes (256 bits) of data per cache line. The data array is not initialized
by a power-on or manual reset.
• LRU (SH7750R only)
In a 2-way set-associative cache, up to 2 items of data can be registered in the cache at each
entry address. When an entry is registered, the LRU bit indicates which of the 2 ways it is to be
registered in. The LRU bit is a single bit of each entry, and its value is controlled by hardware.
The LRU (least-recently-used) algorithm is used for way selection, and selects the less recently
accessed way. The LRU bits are initialized to 0 by a power-on reset but not by a manual reset.
The LRU bits cannot be read or written by software.
R01UH0456EJ0702 Rev. 7.02
Sep 24, 2013
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