MCF548x Reference Manual, Rev. 3
5-16 Freescale Semiconductor

5.5.3.7 MMU Read/Write Tag and Data Entry Registers (MMUTR and MMUDR)

Each TLB entry consists of a 32-bit TLB tag entry and a 32-bit TLB data entry. TLB entries are referenced
through MMUTR and MMUDR. For read TLB accesses, the contents of the TLB tag and data entries
referenced by the allocation address or MMUAR are loaded in MMUTR and MMUDR. TLB write
accesses place MMUTR and MMUDR contents into the TLB tag and data entries defined by the allocation
address or MMUAR.
MMUTR, Figure 5-8, contains the virtual address tag, the address space ID (ASID), a shared page
indicator, and the valid bit.
Table 5-9 describes MMUTR fields.
Table 5-8. MMUAR Field Descriptions
Bits Name Description
31–0 FA Form address. Written by the MMU with the virtual address on DTLB misses and access
faults. For this case, all 32 bits are address bits. This register may be written with a virtual
address and address attribute information for searching the TLB (MMUCR[STLB]). For this
case, FA[31–1] are the virtual page number and FA[0] is the supervisor bit. The current
ASID is used for the TLB search. MMUAR can also be written with a TLB address for use
with the access TLB function (using MMUCR[ACC]).
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
RVA
W
Reset000000000000000 0
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RVA ID SGV
W
Reset000000000000000 0
Reg
Addr
MMUBAR + 0x014
Figure 5-8. MMU Read/Write TLB Tag Register (MMUTR)
Table 5-9. MMUTR Field Descriptions
Bits Name Description
31–10 VA Virtual address. Defines the virtual address mapped by this entry. The number of bits used
in the TLB hit determination depends on the page size field in the corresponding TLB data
entry.
9–2 ID Address space ID (ASID). This extension to the virtual address marks this entry as part of
1 of 256 possible address spaces. Address space 0x00 can be reserved for supervisor
mode. The other 255 address spaces are used to tag user processes. TLB entry ASID
values are compared to the ASID register value for user mode unless the TLB entry is
marked shared (SG = 1). The TLB entry ASID value may be compared to 0x00 for
supervisor accesses or to the ASID. The description of MMUCR[ASM] in Table 5 - 5 gives
details on supervisor mode and ASID compares.