Memory-Mapped Cache Configuration (Sh7750, Sh7750S); Ic Address Array - Hitachi SH7750 Hardware Manual

4.5

Memory-Mapped Cache Configuration (SH7750, SH7750S)

To enable the IC and OC 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. In this case, a branch to the P0, U0, P1, or P3 area should
be made at least 8 instructions after this MOV instruction. The IC and OC are allocated to the P4
area in physical memory space. Only data accesses can be used on both the IC address array and
data array and the OC address array and data array, and accesses are always longword-size.
Instruction fetches cannot be performed in these areas. For reserved bits, a write value of 0 should
be specified; their read value is undefined.
4.5.1

IC Address Array

The IC address array is allocated to addresses H'F000 0000 to H'F0FF FFFF in the P4 area. An
address array access requires a 32-bit address field specification (when reading or writing) and a
32-bit data field specification. The entry to be accessed is specified in the address field, and the
write tag and V bit are specified in the data field.
In the address field, bits [31:24] have the value H'F0 indicating the IC address array, and the entry
is specified by bits [12:5]. CCR.IIX has no effect on this entry specification. The address array bit
[3] association bit (A bit) specifies whether or not association is performed when writing to the IC
address array. As only longword access is used, 0 should be specified for address field bits [1:0].
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 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
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 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 ITLB. If the addresses
match and the V bit is 1, the V bit specified in the data field is written into the IC entry. In
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