Memory Management Unit
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
8-9
Figure 8-4. Two-Level Translation Table (MD_CTR[TWAM] = 1)
When MD_CTR[TWAM] = 1, the tablewalk begins at the level-one base address in M_TWB. EA[0–9]
indicates the level-one page descriptor. As shown in
Table 8-1
, an 8-Mbyte page requires two identical
entries in the level-one table, one for bit 9 = 0 and one for bit 9 = 1.
Table 8-1. Identical Entries Required in Level-One/Level-Two Tables
Page Size
Identical Entries Required in Level-One Table
Identical Entries Required in Level-Two Table
MD_CTR[TWAM] = 0
MD_CTR[TWAM]
= 1
MD_CTR[TWAM] = 0
MD_CTR[TWAM] = 1
1 Kbyte
1
—
1
—
4 Kbytes
1
1
4
1
16 Kbytes
1
1
16
4
512 Kbytes
1
1
1
1
8 Mbytes
8
2
1
1
Level-1 Table Base
Level-1 Index
00
Level-1 Index
0
19 20
31
9 10
Level-2 Index
Page Offset
0
19
Level-1 Table Pointer (M_TWB)
Level-1 Descriptor 0
Level-1 Descriptor 1
Level-1 Descriptor N
Level-1 Descriptor 1023
Level-2 Table Base
Level-2 Index
20-Bit
10-Bit
00
10-Bit
Level-2 Descriptor 0
Level-2 Descriptor 1
Level-2 Descriptor N
Level-2 Descriptor 1023
Physical Page Address
Page Offset
20-Bit
20-Bit
20 for 4 Kbyte
18 for 16 Kbyte
13 for 512 Kbyte
9 for 8 Mbyte
12 for 4 Kbyte
14 for 16 Kbyte
19 for 512 Kbyte
23 for 8 Mbyte
20-Bit
10-Bit
10-Bit
Effective Address
Physical Address
Level-1 Table
Level-2 Table
Summary of Contents for PowerQUICC MPC870
Page 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Page 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Page 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Page 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Page 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Page 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Page 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Page 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Page 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...