SH7727 Datasheet, PDF (184/1109 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7700 Series

Section 3 Memory Management Unit (MMU)
3.4.3 MMU Instruction (LDTLB)
The load TLB instruction (LDTLB) is used to record TLB entries. When the IX bit in MMUCR is
0, the LDTLB instruction changes the TLB entry in the way specified by the RC bit in MMUCR
to the value specified by PTEH and PTEL, using VPN bits 16 to 12 specified in PTEH as the
index number. When the IX bit in MMUCR is 1, the EX-OR of VPN bits 16 to 12 specified in
PTEH and ASID bits 4 to 0 in PTEH are used as the index number.
Figure 3.9 shows the case where the IX bit in MMUCR is 0.
When an MMU exception occurs, the virtual page number of the logical address that caused the
exception is set in PTEH by hardware. The way is set in the RC bit of MMUCR for each
exception according to the rules shown in figure 3.9. Consequently, if the LDTLB instruction is
issued after setting only PTEL in the MMU exception handling routine, TLB entry recording is
possible. Any TLB entry can be updated by software rewriting of PTEH and the RC bits in
MMUCR.
As the LDTLB instruction changes address translation information, there is a risk of destroying
address translation information if this instruction is issued in the P0, U0, or P3 area. Make sure,
therefore, that this instruction is issued in the P1 or P2 area. Also, an instruction associated with an
access to the P0, U0, or P3 area (such as the RTE instruction) should be issued at least two
instructions after the LDTLB instruction.
Rev. 5.00 Dec 12, 2005 page 112 of 1034
REJ09B0254-0500