Double-Precision Floating-Point Subtract
SUBDP
4-79
TMS320C67x Floating-Point Instruction Set
Pipeline
Stage
E1
E2
E3
E4
E5
E6
E7
Read
src1_l
src2_l
src1_h
src2_h
Written
dst_l
dst_h
Unit in use
.L
.L
If
dst is used as the source for the ADDDP, CMPEQDP, CMPLTDP,
CMPGTDP, MPYDP, or SUBDP instruction, the number of delay slots can be
reduced by one, because these instructions read the lower word of the DP
source one cycle before the upper word of the DP source.
Instruction Type
ADDDP/SUBDP
Delay Slots
6
Functional Unit
Latency
2
Example
SUBDP .L1X B1:B0,A3:A2,A5:A4
Before instruction
7 cycles after instruction
B1:B0
4021 3333h
3333 3333h
8.6
B1:B0
4021 3333h
3333 3333h
8.6
A3:A2
C004 0000h
0000 0000h
–2.5
A3:A2
C004 0000h
0000 0000h
–2.5
A5:A4
XXXX XXXXh
XXXX XXXXh
A5:A4
4026 3333h
3333 3333h
11.1
Pipeline