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Memory Management Unit (MMU)
Freescale Semiconductor
4-5
4.2.3
MMU Control Register (MMUCR)
MMUCR contains the address space mode and virtual mode enable bits. The user must force pipeline
synchronization after writing to this register. Therefore, all writes to this register must be immediately
followed by a NOP instruction.
Table 4-3. MMUBAR Field Descriptions
Field
Description
31–16
BA
Base address. Defines the base address for the 64-Kbyte address space mapped to the MMU.
15–1
Reserved, must be cleared.
0
V
Valid. Indicates when MMUMBAR contents are valid. BA is not used unless V is set.
0 MMUBAR contents are not valid.
1 MMUBAR contents are valid.
MMUBAR
Offset:
0x000 (MMUCR)
Access: User read/write
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
R 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
ASM EN
W
Reset 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 4-4. MMU Control Register (MMUCR)
Table 4-4. MMUCR Field Descriptions
Bits
Description
31–2
Reserved, must be cleared.
1
ASM
Address space mode. Controls how the address space ID is used for TLB hits.
0 TLB entry ASID values are compared to the ASID register value for user or supervisor mode unless the TLB entry
is marked shared (MMUTR[SG] = 1). The address space ID register value is the effective address space for all
requests, supervisor and user.
1 Address space 0x00 is reserved for supervisor mode, and the effective address space is forced to 0x00 for all
supervisor accesses. The other 255 address spaces are used to tag user processes. The TLB entry ASID values
are compared to the ASID register for user mode unless the TLB entry is marked shared (SG = 1). The TLB entry
ASID value is always compared to 0x00 for supervisor accesses. This allows two levels of sharing. All users, but
not the supervisor, share an entry if SG is set and ASID does not equal 0. All users and the supervisor share an
entry if SG is set and ASID equals 0
0
EN
Virtual mode enable.
0 Virtual mode is disabled
1 Virtual mode is enabled
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...