Memory Management Unit
MPC885 PowerQUICC Family Reference Manual, Rev. 2
8-12
Freescale Semiconductor
8.7.2
Level-Two Descriptor
Table 8-4
describes the level-two descriptor format supported by hardware. (
Section 8.5, “Protection
Resolution Modes,”
describes the protection modes.)
Table 8-4. Level-Two (Page) Descriptor Format
Bits
Name
Mode 2
Mode 1 or Mode 3
0–19
RPN
Physical (real) page number
20–21
PP
Protection
for 1st
subpage
For Instruction Pages
Supervisor
User
00 No access
No access
01 Executable
No access
1x Executable
Executable
For Data Pages
Supervisor
User
00 No access
No access
01 R/W
No access
10 R/W
R/O
11 R/W
R/W
For Instruction Pages
Supervisor
User
Extended encoding:
00 No access
No access
01 Executable No access
1x Reserved
Basic encoding:
00 Executable No access
01 Executable Executable
1x Executable Executable
For Data Pages
Supervisor
User
Extended encoding:
00 No access
No access
01 R/O
No access
1x Reserved
Basic encoding:
00 R/W
No access
01 R/W
R/O
10 R/W
R/W
11 R/O
R/O
22
PP
1
1
For pages larger than 4 Kbytes in mode 2, PP in bits [22–23,24–25,26–27] must equal the PP in bits [20–21].
2nd
subpage
0 Bits 20–21 contain Basic encoding
1 Bits 20–21 contain extended encoding
23
C—Change bit for entry. Set to 1 by default if change
tracking functionality is not desired.
0 Unchanged region (write-protected)
1 Changed region, write allowed
24–25
3rd
subpage
MD_CTR[PPCS] = 0.
For 1-Kbyte pages in mode
3, program to the
appropriate subpage
validity. For mode 1,
program to 0b1111.
MD_CTR[PPCS] = 1 (mode
1 only)
1000 Hit (supervisor
accesses only)
0100 Hit (user accesses
only)
1100 Hit for both
26–27
4th
subpage
28
SPS
Small page size. Used with the level-one (L1) descriptor’s page-size (PS) field; see
Section 8.7.3,
“Page Size
.”
0 4 Kbyte
1 16 Kbyte or larger (512 Kbyte or 8 Mbyte)
29
SH
Shared page
0 Entry matches only if a TLB entry’s ASID field matches the value in M_CASID.
1 ASID comparison is disabled for the entry.
30
CI
Cache-inhibit attribute for the entry.
0 Caching is allowed.
1 Caching is inhibited.
31
V
Page valid bit
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Страница 1172: ...SEC Lite Overview MPC885 PowerQUICC Family Reference Manual Rev 2 46 8 Freescale Semiconductor ...
Страница 1176: ...SEC Lite Address Map MPC885 PowerQUICC Family Reference Manual Rev 2 47 4 Freescale Semiconductor ...
Страница 1214: ...SEC Lite Execution Units MPC885 PowerQUICC Family Reference Manual Rev 2 48 38 Freescale Semiconductor ...
Страница 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Страница 1313: ...MPC885 PowerQUICC Family Reference Manual Rev 2 Freescale Semiconductor B 1 Appendix B Serial Communications Performance TBD ...
Страница 1314: ...Serial Communications Performance MPC885 PowerQUICC Family Reference Manual Rev 2 B 2 Freescale Semiconductor ...
Страница 1320: ...Register Quick Reference Guide MPC885 PowerQUICC Family Reference Manual Rev 2 C 6 Freescale Semiconductor ...
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