SH7708 datasheet(117/633 Pages) RENESAS

117 / 633 page

In RAM mode, two ways are used as cache (way 0 and way 1). Bit 5 of the LRU bits indicates

which way is to be replaced. When bit 5 is 0, way 1 is to be replaced. When bit 5 is 1, way 0 is to

be replaced.

The LRU bits are initialized to 0 by a power-on reset, but are not initialized by a manual reset.

Table 5.2

LRU and Way Replacement in Normal Mode

LRU (5–0)

Way to be Replaced

000000, 000100, 010100, 100000, 110000, 110100

000001, 000011, 001011, 100001, 101001, 101011

000110, 000111, 001111, 010110, 011110, 011111

111000, 111001, 111011, 111100, 111110, 111111

5.1.3

Table 5.3 shows details of the cache control register.

Table 5.3

Abbr.

R/W

Size

Initial Value*

Address

Cache control register

CCR

R/W

Longword

H'00000000

H'FFFFFFEC

Note: * Initialized by a power-on reset or manual reset.

5.2

5.2.1

Cache Control Register (CCR)

The cache is enabled or disabled using the CE bit of the cache control register (CCR). CCR also

has an RA bit (which switches the cache operation mode between RAM mode and normal mode),

a CF bit (which invalidates all cache entries), a WT bit and a CB bit* (which selects either write-

through mode or write-back mode). Programs that change the contents of the CCR register should

be placed in address space that is not cached. When updating the contents of the CCR register,

always set bit 4 to 0. Figure 5.2 shows the configuration of the CCR register. CB bit is not

supported in emulator.

Note: * SH7708S, SH7708R Only

SH7708 Scheda tecnica(PDF) 117 Page - Renesas Technology Corp