SH7721 datasheet(267/1524 Pages) RENESAS

267 / 1524 page

Section 5 Cache

Rev. 3.00 Jan. 18, 2008 Page 205 of 1458

REJ09B0033-0300

5.3

Operation

5.3.1

Searching the Cache

If the cache is enabled (the CE bit in CCR1 = 1), whenever instructions or data in spaces P0, P1,

P3, and U0 are accessed the cache will be searched to see if the desired instruction or data is in the

cache. Figure 5.2 illustrates the method by which the cache is searched. The cache is a physical

cache and holds physical addresses in its address section. The example of operation in 16-kbyte

mode is described below:

Entries are selected using bits 11 to 4 of the address (virtual) of the access to memory and the tag

address of that entry is read. In parallel with reading the tag address, the virtual address is

converted into the physical address. The virtual address of the access to memory and the physical

address (tag address) read from the address array are compared. The address comparison uses all

four ways. When the comparison shows a match and the selected entry is valid (V = 1), a cache hit

occurs. When the comparison does not show a match or the selected entry is not valid (V = 0), a

cache miss occurs. Figure 5.2 shows a hit on way 1.

SH7721 Datasheet(PDF) 267 Page - Renesas Technology Corp