ARM ARM1176JZF-S User Manual

Memory Management Unit
ARM DDI 0301H Copyright © 2004-2009 ARM Limited. All rights reserved. 6-50
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Figure 6-16 4KB small page or 1KB small subpage translations, backwards-compatible format
Using backwards-compatible descriptors, the 4KB small page is generated by setting all of the
AP bit pairs to the same values, AP3=AP2=AP1=AP0. If any one of the pairs are different, then
the 4KB small page is converted into four 1KB small page subpages. The subpage access
permission bits are chosen using the virtual address bits [11:10].
Second-level extended small page table walk
If bits [1:0] of the second-level descriptor are b1XN for ARMv6 format descriptors, or b11 for
backwards-compatible descriptors, then an extended small page table walk is required.
Figure 6-17 on page 6-51 shows the translation process for a 4KB extended small page using
ARMv6 format descriptors, AP bits disabled.
N
S
1
Coarse page table base address
31 1098 54 210
P Domain 0
First-level table index
31 20 19 12 11 0
Second-level
table index
Page index
Translation base
31 14 13 0
0
Small page base address
31 1211109876543210
AP
3
AP
2
AP
1
AP
0
C B 1
0
Coarse page table base address
31 10 9 2 1 0
Second-level table
index
0
0
Translation base
31 14 13 0
First-level table index 0
21
Page index
Page base address
31 12 11 0
Second-level descriptor address
Second-level descriptor
Physical address
First-level descriptor
First-level descriptor address
Modified virtual address
Translation table base
3
SBZ SBZ

ARM ARM1176JZF-S Specifications

General

Brand	ARM
Model	ARM1176JZF-S
Category	Computer Hardware
Language	English