NEC Network Controller uPD98502 - Manual (Page 170)

CHAPTER 2 V R 4120A
170 Preliminary User’s Manual S15543EJ1V0UM
Figure 2-67. Instruction Cache Line Format
22 21
V PTag
0
1 22
Data
0
Data
Data
Data
31
PTag : Physical tag (bits 31 to 10 of physical address)
V
: Valid bit
Data : Cache data
2.7.2.2 Organization of the data cache (D-cache)
Each line of D-cache data has an associated 25-bit tag that contains a 22-bit physical address, a Valid bit, a Dirty
bit, and a Write-back bit.
The V R 4120A Core D-cache has the following characteristics :
— write-back
— direct-mapped
— indexed with a virtual address
— checked with a physical tag
— organized with a 4-word (16-byte) cache line.
Figure 2-68 shows the format of a 4-word (16-byte) D-cache line.
Figure 2-68. Data Cache Line Format
W V D PTag
Data
Data
24 23 22 21 0
0 63
1 1 1 22
W : Write-back bit (set if cache line has been written)
D : Dirty bit
V : Valid bit
PTag : Physical tag (bits 31 to 10 of physical address)
Data
: D-cache data