Table of Contents
Advertisement
Software Processing (Initial Page Write Exception Handling Routine): The following
processing should be carried out as the responsibility of software:
1. Retrieve the necessary page table entry from external memory.
2. Write 1 to the D bit in the external memory page table entry.
3. Write to PTEL the values of the PPN, PR, SZ, C, D, WT, SH, and V bits in the page table
entry recorded in external memory. If necessary, the values of the SA and TC bits should be
written to PTEA.
4. When the entry to be replaced in entry replacement is specified by software, write that value to
URC in the MMUCR register. If URC is greater than URB at this time, the value should be
changed to an appropriate value after issuing an LDTLB instruction.
5. Execute the LDTLB instruction and write the contents of PTEH, PTEL, and PTEA to the
UTLB.
6. Finally, execute the exception handling return instruction (RTE), terminate the exception
handling routine, and return control to the normal flow. The RTE instruction should be issued
at least one instruction after the LDTLB instruction.
3.7
Memory-Mapped TLB Configuration
To enable the ITLB and UTLB to be managed by software, their contents can be read and written
by a P2 area program with a MOV instruction in privileged mode. Operation is not guaranteed if
access is made from a program in another area. A branch to an area other than the P2 area should
be made at least 8 instructions after this MOV instruction. The ITLB and UTLB are allocated to
the P4 area in physical memory space. VPN, V, and ASID in the ITLB can be accessed as an
address array, PPN, V, SZ, PR, C, and SH as data array 1, and SA and TC as data array 2. VPN,
D, V, and ASID in the UTLB can be accessed as an address array, PPN, V, SZ, PR, C, D, WT, and
SH as data array 1, and SA and TC as data array 2. V and D can be accessed from both the address
array side and the data array side. Only longword access is possible. Instruction fetches cannot be
performed in these areas. For reserved bits, a write value of 0 should be specified; their read value
is undefined.
Rev. 4.0, 04/00, page 54 of 850
Advertisement
Table of Contents
