Digi NS9215 User Manual
Page 96
W O R K I N G W I T H T H E C P U
R7:Cache Operations register
96
Hardware Reference NS9215
Modified virtual
address format
(MVA)
This is the modified virtual address format for
Rd
for the CP15 R7
MCR
operations.
The tag, set, and word fields define the MVA.
For all cache operations, the word field
SHOULD BE ZERO
.
Set/Way format
This is the Set/Way format for
Rd
for the CP15 R7
MCR
operations.
A and S are the base-two logarithms of the associativity and the number of
sets.
The set, way, and word files define the format.
For all of the cache operations, word
SHOULD BE ZERO
.
Set/Way example
For example, a 16 KB cache, 4-way set associative, 8-word line results in the
following:
A = log
2
associativity = log
2
4 = 2
S = log
2
NSETS where
NSETS = cache size in bytes/associativity/line length in bytes:
NSETS = 16384/4/32 = 128
Result: S = log
2
128 = 7
Test and clean
DCache
instructions
The test and clean DCache instruction provides an efficient way to clean the entire
DCache, using a simple loop. The test and clean DCache instruction tests a number
of lines in the DCache to determine whether any of them are dirty. If any dirty lines
are found, one of those lines is cleaned. The test and clean DCache instruction also
returns the status of the entire DCache in bit 30.
Drain write buffer
SBZ
MCR p15, 0, Rd, c7, c10, 4
Wait for interrupt
SBZ
MCR p15, 0, Rd, c7, c0, 4
Function/operation
Data format
Instruction
31
0
S+4
4
SBZ
Set(=index)
Word
Tag
2 1
5
S+5
31
0
S+4
4
SBZ
Set(=index)
Word
SBZ
2 1
5
S+5
Way
32-A 31-A