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The following three kinds of operation can be used on the OC address array:
1. OC address array read
The tag, U bit, and V bit are read into the data field from the OC entry corresponding to the
entry set in the address field. In a read, associative operation is not performed regardless of
whether the association bit specified in the address field is 1 or 0.
2. OC address array write (non-associative)
The tag, U bit, and V bit specified in the data field are written to the OC entry corresponding to
the entry set in the address field. The A bit in the address field should be cleared to 0.
When a write is performed to a cache line for which the U bit and V bit are both 1, after write-
back of that cache line, the tag, U bit, and V bit specified in the data field are written.
3. OC address array write (associative)
When a write is performed with the A bit in the address field set to 1, the tag stored in the entry
specified in the address field is compared with the tag specified in the data field. If the MMU
is enabled at this time, comparison is performed after the virtual address specified by data field
bits [31:10] has been translated to a physical address using the UTLB. If the addresses match
and the V bit is 1, the U bit and V bit specified in the data field are written into the OC entry.
This operation is used to invalidate a specific OC entry. If the OC entry U bit is 1, and 0 is
written to the V bit or to the U bit, write-back is performed. If an UTLB miss occurs during
address translation, or the comparison shows a mismatch, no operation results and the write is
not performed. If a data TLB multiple hit exception occurs during address translation,
processing switches to the data TLB multiple hit exception handling routine.
31
Address field
1 1 1 1 0 1 0 0
31
Data field
V
: Validity bit
U
: Dirty bit
A
: Association bit
: Reserved bits (0 write value, undefined read value)
24
23
Tag address
Figure 4.8 Memory-Mapped OC Address Array
14
13
Entry
10 9
Rev. 2.0, 03/99, page 77 of 396
5 4 3 2 1 0
A
2
1 0
U
V
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