SH7708 datasheet(95/633 Pages) RENESAS

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3.6

Memory-Mapped TLB

In order for TLB operations to be managed by software, TLB contents can be read or written to in

privileged mode using the MOV instruction. The TLB is assigned to the P4 area in virtual address

space. The TLB address array (VPN, V bit, and ASID) is assigned to H'F2000000–H'F2FFFFFF,

and the data array (PPN, PR, SZ, C, D, and SH bits) to H'F3000000–H'F3FFFFFF. The V bit in

the address array can also be accessed from the data array. Only longword access is possible for

both the address array and the data array.

3.6.1

Address Array

The address array is assigned to H'F2000000 to H'F2FFFFFF. To access an address array, the

32-bit address field (for read/write operations) and 32-bit data field (for write operations) must be

specified. The address field specifies information for selecting the entry to be accessed; the data

field specifies the VPN, V bit and ASID to be written to the address array (figure 3.14 (1)).

In the address field, specify the entry address for selecting the entry (bits 16–12), W for selecting

the way (bits 9–8: 00 is way 0, 01 is way 1, 10 is way 2, 11 is way 3) and H'F2 to indicate address

array access (bits 31–24). The IX bit in MMUCR indicates whether an EX-OR is taken of the

entry address and ASID.

When writing, specify bit 7 as the A bit. The A bit indicates whether addresses are compared

during writing. When the A bit is 1, the VPNs of the four entries selected by the entry addresses

are compared to the VPN to be written into the address array specified in the data field. Writing

takes place to the way that has a hit. When a miss occurs, nothing is written to the address array

and no operation occurs. The way number specified in bits 9–8 is not used. The item compared is

determined by the SZ and SH bits of the entry selected by the entry address, the SV bit in

MMUCR and the MD bit in SR, just as in ordinary operations (see section 3.3.3).

When the A bit is 0, it is written to the entry selected with the entry address and way number

without comparing addresses.

When reading, the VPN (31–17, 11–10), V bit, and ASID of the entry specified by the entry

address and way number are read in the format of the data field in figure 3.14 without comparing

addresses. Zero is read in the data field (16–12).

To invalidate a specific entry, specify the entry and write 0 to its V bit. When 1 is specified for the

A bit, only the required VPN entry is invalidated.

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