SLIDE 88 IWSSIP 2014
88 Modulo- ππ β ππ β π Parallel Prefix Addition via Excess-Modulo Encoding of Residue Modulo- ππ β ππ β π Parallel Prefix Addition via Excess-Modulo Encoding of Residue
ARITH 22
13
- How to solve Carry Save Stage Delay problem?
ππβπ β¦ ππ ππβπ β¦ ππ ππ ππβπ β¦ ππ ππβπ β¦ ππ ππ π π πβ² ππβπ β¦ ππ ππβπ β¦ ππ ππ πβ²β² ππβπ β¦ ππβπ β¦ ππ ππ πΊ ππ©π« π π
- Finding a relative between the π», π of π + π 2πβ2πβ1 and π»β², πβ² of πβ² + πβ²β² 2πβ2πβ1
ππ = ππβ1 β¨ π»πβ1:0
β²
, if π = 0 π»πβ1:0
β²
β¨ π
πβ1:0 β²
(ππβ1 β¨ π»πβ1:0
β²
), if 1 β€ π β€ π βπ β¨ π ππ β¨ βππ, if π = π + 1 π»πβ1:π+1
β²
β¨ ππβ1:π+1
β²
ππ+1, if π > π + 1 ππ = π»πβ1:0, if π = 0 π»πβ1:0 β¨ ππβ1:0π»πβ1:0, if 1 β€ π β€ π βππ»πβ1:0 β¨ π
π:0 β²β² π»πβ1:0,
if π = π + 1 βπβ1π»πβ2:0 β¨ ππβ1:0
β²β²
π»πβ1:0, if π > π + 1 (π―π:π+π
β²
, πΈπ:π+π
β²
ππ) = (πππ―πβπ:π, π°π:π) π β₯ π ππ:0
β²β² = βπ β¨ ππβ1:0 β¨ π»πβ1:0
ππβ1:0
β²β²
= πβ²πβ1:π+1π
π:0 β²β²
(π», π) (π»β², πβ²)
The carry-save stage is effectively off the critical delay path