Level 1 Memory System
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
6-16
ID021414
Non-Confidential
Table 6-10
shows the tag and valid bits format for the selected cache line using only Data
Register 0.
The CP15 Instruction Cache Data Read Operation returns two entries from the cache in Data
Register 0 and Data Register 1 corresponding to the 16-bit aligned offset in the cache line:
Data Register 0
Bits[19:0] data from cache
0b00
.
Data Register 1
Bits[19:0] data from cache
0b10
.
In A32 or A64 state these two fields combined always represent a single pre-decoded
instruction. In T32 state, they can represent any combination of 16-bit and partial or full 32-bit
instructions.
6.7.3
TLB RAM accesses
The Cortex-A53 processor unified TLB is built from a 4-way set-associative RAM based
structure. To read the individual entries into the data registers software must write to the TLB
Data Read Operation Register.
Table 6-11
shows the write TLB Data Read Operation Register
location encoding of Rd.
Table 6-10 Instruction cache tag data format
Bits
Description
[31]
Parity
a
.
a. Parity bit is not available for a CP15
Instruction cache Tag Read Operation.
In this case, this bit is
1'b0
.
[30:29]
Valid and set mode:
0b00
A32.
0b01
T32.
0b10
A64.
0b11
Invalid.
[28]
Non-secure state (NS).
[27:0]
Tag address.
Table 6-11 TLB Data Read Operation Register location encoding
Bits
Description
[31:30] TLB
way
[29:8] Unused
[7:0] TLB
index