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3.5
MMU Functions
3.5.1
MMU Hardware Management
The SH7750 Series supports the following MMU functions.
1. The MMU decodes the virtual address to be accessed by software, and performs address
translation by controlling the UTLB/ITLB in accordance with the MMUCR settings.
2. The MMU determines the cache access status on the basis of the page management
information read during address translation (C, WT, SA, and TC bits).
3. If address translation cannot be performed normally in a data access or instruction access, the
MMU notifies software by means of an MMU exception.
4. If address translation information is not recorded in the ITLB in an instruction access, the
MMU searches the UTLB, and if the necessary address translation information is recorded in
the UTLB, the MMU copies this information into the ITLB in accordance with
MMUCR.LRUI.
3.5.2
MMU Software Management
Software processing for the MMU consists of the following:
1. Setting of MMU-related registers. Some registers are also partially updated by hardware
automatically.
2. Recording, deletion, and reading of TLB entries. There are two methods of recording UTLB
entries: by using the LDTLB instruction, or by writing directly to the memory-mapped UTLB.
ITLB entries can only be recorded by writing directly to the memory-mapped ITLB. For
deleting or reading UTLB/ITLB entries, it is possible to access the memory-mapped
UTLB/ITLB.
3. MMU exception handling. When an MMU exception occurs, processing is performed based on
information set by hardware.
3.5.3
MMU Instruction (LDTLB)
A TLB load instruction (LDTLB) is provided for recording UTLB entries. When an LDTLB
instruction is issued, the SH7750 Series copies the contents of PTEH, PTEL, and PTEA to the
UTLB entry indicated by MMUCR.URC. ITLB entries are not updated by the LDTLB instruction,
and therefore address translation information purged from the UTLB entry may still remain in the
ITLB entry. As the LDTLB instruction changes address translation information, ensure that it is
issued by a program in the P1 or P2 area. The operation of the LDTLB instruction is shown in
figure 3.12.
Rev. 4.0, 04/00, page 45 of 850
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