
Spartan-3E FPGA Family: DC and Switching Characteristics
DS312 (v4.1) July 19, 2013
Product Specification
138
18 x 18 Embedded Multiplier Timing
Table 102: 18 x 18 Embedded Multiplier Timing
Symbol
Description
Speed Grade
Units
-5
-4
MinMax
Combinatorial Delay
TMULT
Combinatorial multiplier propagation delay from the A and B inputs
to the P outputs, assuming 18-bit inputs and a 36-bit product
(AREG, BREG, and PREG registers unused)
ns
Clock-to-Output Times
TMSCKP_P
Clock-to-output delay from the active transition of the CLK input to
valid data appearing on the P outputs when using the PREG
-0.98
-1.10
ns
TMSCKP_A
TMSCKP_B
Clock-to-output delay from the active transition of the CLK input to
valid data appearing on the P outputs when using either the AREG
-4.42
-4.97
ns
Setup Times
TMSDCK_P
Data setup time at the A or B input before the active transition at the
CLK when using only the PREG output register (AREG, BREG
3.54
-3.98
-ns
TMSDCK_A
Data setup time at the A input before the active transition at the
0.20
-0.23
-ns
TMSDCK_B
Data setup time at the B input before the active transition at the
0.35
-0.39
-ns
Hold Times
TMSCKD_P
Data hold time at the A or B input after the active transition at the
CLK when using only the PREG output register (AREG, BREG
–0.97
-
–0.97
-ns
TMSCKD_A
Data hold time at the A input after the active transition at the CLK
0.03
-0.04
-ns
TMSCKD_B
Data hold time at the B input after the active transition at the CLK
0.04
-0.05
-ns
Clock Frequency
FMULT
Internal operating frequency for a two-stage 18x18 multiplier using
the AREG and BREG input registers and the PREG output
02700240
MHz
Notes:
1.
Combinatorial delay is less and pipelined performance is higher when multiplying input data with less than 18 bits.
2.
The PREG register is typically used in both single-stage and two-stage pipelined multiplier implementations.
3.
Input registers AREG or BREG are typically used when inferring a two-stage multiplier.