HD6417660 RENESAS [Renesas Technology Corp], HD6417660 Datasheet - Page 221

• Manufacturer Part Number: HD6417660
• Description: Renesas 32-Bit RISC Microcomputer
• Manufacturer: RENESAS [Renesas Technology Corp]

5.3
5.3.1
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.
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. The virtual address (bits 31 to 10) 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.
31
Operation
Searching the Cache
Virtual address
CMP0: Comparison circuit 0
CMP1: Comparison circuit 1
CMP2: Comparison circuit 2
CMP3: Comparison circuit 3
Address for accessing
memory (bits 31 to 10)
Entry selection
12 11
255
CMP0 CMP1 CMP2 CMP3
0
1
V U Tag address
Hit signal 1
Figure 5.2 Cache Search Scheme
4 3 2 1 0
Ways 0 to 3
Longword (LW) selection
LW0
LW1
Rev. 1.00, 02/04, page 183 of 804
LW2
Ways 0 to 3
LW3