CLR
Clear a Bit Field
3-78
Instruction Set
SPRU733
Description
The field in
src2
, specified by
csta
and
cstb
, is cleared to zero.
csta
and
cstb
may be specified as constants or as the ten LSBs of the
src1
registers, with
cstb
being bits 0
−
4 and
csta
bits 5
−
9.
csta
signifies the bit location of the LSB
in the field and
cstb
signifies the bit location of the MSB in the field. In other
words,
csta
and
cstb
represent the beginning and ending bits, respectively, of
the field to be cleared. The LSB location of
src2
is 0 and the MSB location of
src2
is 31. In the example below,
csta
is 15 and
cstb
is 23. Only the ten LSBs
are valid for the register version of the instruction. If any of the 22 MSBs are
non-zero, the result is invalid.
src2
dst
0
x x x x x x x x
x x x x x x x x x x x x x x x
1
1
1 1
1
0
0
0
0
x x x x x x x x
x x x x x x x x x x x x x x x
0
0
0 0
0
0
0
0
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
csta
cstb
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
Execution
If the constant form is used:
if (cond)
src2
clear
csta
,
cstb
→
dst
else nop
If the register form is used:
if (cond)
src2
clear
src1
9..5
,
src1
4..0
→
dst
else nop
Pipeline
Stage
E1
Read
src1, src2
Written
dst
Unit in use
.S
Instruction Type
Single-cycle
Delay Slots
0
See Also
SET
Pipeline