SH7785 Datasheet, PDF (263/1692 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

8. Caches
In the data field, the tag is indicated by bits [31:10], and the V bit by bit [0]. As the IC address
array tag is 19 bits in length, data field bits [31:29] are not used in the case of a write in which
association is not performed. Data field bits [31:29] are used for the virtual address specification
only in the case of a write in which association is performed.
The following three kinds of operation can be used on the IC address array:
1. IC address array read
The tag and V bit are read into the data field from the IC entry corresponding to the way and
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. IC address array write (non-associative)
The tag and V bit specified in the data field are written to the IC entry corresponding to the
way and entry set in the address field. The A bit in the address field should be cleared to 0.
3. IC address array write (associative)
When a write is performed with the A bit in the address field set to 1, the tag in each way
stored in the entry specified in the address field is compared with the tag specified in the data
field. The way numbers of bits [14:13] in the address field are not used. 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 ITLB. If the addresses match and
the V bit in the way is 1, the V bit specified in the data field is written into the IC entry. In
other cases, no operation is performed. This operation is used to invalidate a specific IC entry.
If an ITLB miss occurs during address translation, or the comparison shows a mismatch, an
exception is not generated, no operation is performed, and the write is not executed.
Note: IC address array associative writing function may not be supported in the future SuperH
Series. Therefore, it is recommended that the ICBI instruction should be used to operate
the IC definitely by handling ITLB miss and reporting ITLB miss exception.
31
24 23
151413 12
Address field _{1 1 1 1 0 0 0 0 * * * * * * * * *}
Entry
31
Data field
Way
10 9
Tag
543210
0A 0 0 0
10
V
V : Validity bit
A : Association bit
: Reserved bits (write value should be 0 and read value is undefined )
* ^{: Don't care}
Figure 8.5 Memory-Mapped IC Address Array (Cache size = 32 Kbytes)
Rev.1.00 Jan. 10, 2008 Page 233 of 1658
REJ09B0261-0100