7: Memory Management Unit
7-10 EPSON ARM720T CORE CPU MANUAL
7.3.7 Translating section references
Figure 7-8 shows the complete section translation sequence.
Figure 7-8 Section translation
Note: You must check access permissions contained in the level one descriptor before
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.
Figure 7-9 Level two descriptor
31 14 13 0
Translation base
31 14 13 2 1 0
00
Table indexTranslation base
Modified virtual address
Translation table base
31 2019 0
Table index Section index
31 2019 0
Section indexSection base address
Section level one descriptor
Physical address
31 2019 0
Section base address AP
Domain
1CB10
2134589101112
31 12111098 543210
00
Large page base address 0 1
Small page base address C B 1 0
Tiny page base address 1 1
Fault
Large page
Small page
Tiny page
7616 15
BC
CB
ap0
ap0
ap
ap1ap2ap3
ap1ap2ap3
