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31
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Coarse page table base address
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Coarse page table base address
31
31
Figure 6-16 4KB small page or 1KB small subpage translations, backwards-compatible format
ARM DDI 0301H
ID012310
Translation table base
Translation base
First-level descriptor address
Translation base
First-level descriptor
Second-level descriptor address
Second-level descriptor
Small page base address
Physical address
Page base address
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.
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14 13
Modified virtual address
31
20 19
First-level table index
14 13
First-level table index
10 9 8
5 4
3
N
P Domain
S
SBZ
10 9
Second-level table
index
12 11 10 9 8 7 6 5 4 3 2 1 0
AP
AP
AP
AP
C B 1
3
2
1
0
12 11
Page index
Memory Management Unit
0
12 11
Second-level
table index
2 1
0
0
0
2 1 0
0
1
SBZ
2 1 0
0
0
0
0
0
Page index
6-50
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