Level 1 Memory System
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
6-17
ID021414
Non-Confidential
The TLB RAM contains the data for the main TLB, the walk cache, and the
Intermediate
Physical Address
(IPA) cache RAMs.
Table 6-12
shows the TLB indexes that determines the
format of the TLB RAM accesses.
Main TLB RAM
The main TLB RAM uses a 117-bit encoding:
Data Register 0[31:0]
TLB Descriptor[31:0].
Data Register 1[31:0]
TLB Descriptor[63:32].
Data Register 2[31:0]
TLB Descriptor[95:64].
Data Register 3[20:0]
TLB Descriptor[116:96].
Table 6-13
shows the data fields in the TLB descriptor.
Table 6-12 TLB RAM format
TLB index[7:0]
Format
0-127
Main TLB RAM, see
Main TLB RAM
128-143
Walk cache RAM, see
Walk cache RAM
on page 6-20
144-159
IPA cache RAM, see
IPA cache RAM
on page 6-21
160-255
Unused
Table 6-13 Main TLB descriptor data fields
Bits
Name
Description
[116:114]
Parity
ECC inclusion is processor configuration dependent. If ECC is not configured, these
bits are absent.
[113:112]
S2 Level
The stage 2 level that gave this translation:
0b00
No stage 2 translation performed.
0b01
Level 1.
0b10
Level 2.
0b11
Level 3.
[111:109]
S1 Size
The stage 1 size that gave this translation:
0b000
4KB.
0b001
64KB.
0b010
1MB.
0b011
2MB.
0b100
16MB.
0b101
512MB.
0b110
1GB.
[108:105]
Domain
Valid only if the entry was fetched in VMSAv7 format.
[104:97]
Memory Type and shareability
See
Table 6-14 on page 6-18
.
[96]
XS2
Stage2 executable permissions.
[95]
XS1Nonusr
Non user mode executable permissions.
[94]
XS1Usr
User mode executable permissions.
[93:66]
PA
Physical Address.