Memory Management Unit
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
8-23
Table 8-15
describes M_CASID fields.
8.8.10
MMU Access Protection Registers (MI_AP/MD_AP)
The IMMU access protection register (MI_AP, SPR 786) contains the settings for the access protection
groups for the IMMU. The DMMU access protection register (MD_AP, SPR 794) is identical. Both
registers are shown in
Figure 8-15
.
MI_AP/MD_AP fields are described in
Table 8-16
.
8.8.11
MMU Tablewalk Special Register (M_TW)
The MMU tablewalk special register (M_TW), shown in
Figure 8-16
, is a scratch register used by
tablewalk exception handlers.
Table 8-15. M_CASID Field Descriptions
Bits
Name
Description
0–27
—
Reserved. Ignored on write, returns 0 on read
28–31
CASID
Current address space ID. Compared with ASID field of a TLB entry to qualify a match
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Field GP0 GP1 GP2 GP3 GP4
GP5
GP6
GP7
GP8
GP9 GP10 GP11 GP12 GP13 GP14 GP15
Reset
—
R/W
R/W
SPR
786 (MI_AP); 794 (MD_AP)
Figure 8-15. MMU Access Protection Registers (MI_AP/MD_AP)
Table 8-16. MI_AP/MD_AP Field Descriptions
Bits
Name
Domain Manager Mode (M
x_CTR[GPM] = 1)
Default Mode (M
x_CTR[GPM] = 0)
0–1
GP
x
GP
00 No access
01 Client–access permission defined by page
protection bits
10 Reserved
11 Manager–free access
GP = Ks/Kp as defined by PowerPC architecture
00 All accesses are treated as supervisor
01 Access permission defined by page
protection bits
10 User and supervisor interpretation is
swapped
11 All accesses are treated as user
2–3
…
30–31
0
31
Reset
—
R/W
R/W
SPR
799
Figure 8-16. MMU Tablewalk Special Register (M_TW)
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