Digi NS9750 - Manual (Page 112)

M e m o r y M a n a g e m e n t U n i t ( M M U )
8 8 N S 9 7 5 0 H a r d w a r e R e f e r e n c e
Fine page table descriptor
A fine page table descriptor provides the base address of a page table that contains
second-level descriptors for large page, small page, or tiny page accesses. Fine page
tables have 1024 entries, splitting the 1 MB that the table describes into 1 KB blocks.
Figure 30 shows the format of a fine page table descriptor. Table 36 describes the fine
page table descriptor bit assignments.
Note:
If a fine page table descriptor is returned from the first-level fetch, a
second-level fetch is initiated.
Figure 30: Fine page table descriptor
[1:0] Must be 01 to indicate a coarse page descriptor.
Bits Description
[31:12] Forms the base for referencing the second-level descriptor (the fine page table index for
the entry is derived from the MVA).
[11:9] Always written as 0.
[8:5] Specifies one of the 16 possible domains (held in the Domain Access Control register) that
contain primary access controls.
4 Always written as 1.
[3:2} Always written as 0.
[1:0] Must be 11 to indicate a fine page table descriptor.
Table 36: Fine page table descriptor bits
Bits Description
Table 35: Coarse page table descriptor bits
Fine page table base address SBZ Domain 1 1 1
1 0 2 3 4 5 8 9 11 12 31
SBZ