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7: Memory Management Unit
7.3.7
Translating section references
Figure 7-8 shows the complete section translation sequence.
31
31
31
Section base address
31
Section base address
You must check access permissions contained in the level one descriptor before
Note:
generating the physical address.
7.3.8
Level two descriptor
If the level one fetch returns either a coarse page table descriptor or a fine page table
descriptor, this provides the base address of the page table to be used. The page table is then
accessed and a level two descriptor is returned. Figure 7-9 shows the format of level two
descriptors.
31
Large page base address
Small page base address
Tiny page base address
7-10
Translation table base
Translation base
Translation base
Section level one descriptor
20 19
Physical address
20 19
Figure 7-8 Section translation
16 15
Figure 7-9 Level two descriptor
Modified virtual address
31
20 19
Table index
14 13
14 13
2 1 0
Table index
12
11
10
9
8
5
4
3
2 1
Domain 1 C B 1 0
AP
Section index
12 11 10 9 8
7 6
ap3
ap2
ap1
ap3
ap2
ap1
EPSON
Section index
0
0 0
0
0
5 4 3 2 1 0
0 0
Fault
Large page
ap0
C B
0 1
Small page
ap0
C B 1 0
Tiny page
ap
C
B
1 1
ARM720T CORE CPU MANUAL
0
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