
10-12
ColdFire CF4E Core User’s Manual
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MMU Definition
The address space ID (ASID) is located in a CPU space control register. The 8-bit ASID
value located in the low order byte of a 32-bit supervisor control register, mapped into CPU
space at address 0x003 and accessed using a MOVEC instruction. The
ColdFire Family
Programmer’s Reference Manual
describes MOVEC.
This 8-bit field is the current user ASID. The ASID is an extension to the virtual address.
Address space 0x00 may be reserved for supervisor mode. See address space mode
functionality in Section 10.5.3.3, “MMU Control Register (MMUCR).” The other 255
address spaces are used to tag user processes. The TLB entry ASID values are compared to
this value for user mode unless the TLB entry is marked shared (MMUTR[SG] is set). The
TLB entry ASID value may be compared to 0x00 for supervisor accesses.
10.5.3.3
MMU Control Register (MMUCR)
MMUCR, Figure 10-4, has 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 10-5 describes MMUCR fields.
Table 10-4. MMU Memory Map
Offset from MMUBAR
Name
+ 0x0000
MMU control register (MMUCR)
+ 0x0004
MMU operation register (MMUOR)
+ 0x0008
MMU status register (MMUSR)
+ 0x000C
Reserved
+ 0x0010
MMU fault, test, or TLB address register (MMUAR)
+ 0x0014
MMU read/write TLB tag register (MMUTR)
+ 0x0018
MMU read/write TLB data register (MMUDR)
+ 0x001C–0xFFFC
Reserved
1
1
May be used for implementation-specific information/control registers.
31
2
1
0
Field
—
ASM EN
Reset
—
0
R/W
R/W
Rc
0x000
Figure 10-4. MMU Control Register (MMUCR)
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