Altera Stratix - Four-Multiplier Adder Mode

6–24 Altera Corporation
Stratix Device Handbook, Volume 2 July 2005
Operational Modes
Figure 6–13. Complex Multiplier Implemented Using Two-Multiplier Adder
Mode
Four-Multiplier Adder Mode
In the four-multiplier adder mode, which you can use for 1-dimensional
and 2-dimensional filtering applications, the DSP block adds the results
of two adder/subtractor/accumulators in a final stage (the summation
block).
1 You can only use the adder block if it follows multiplication
operations.
9- & 18-Bit Summation Blocks
A single DSP block can implement one 18 × 18 or two 9 × 9 summation
blocks (see Figure 6–14 on page 6–25). The multiplier product widths
must be the same size.
Subtractor
36
36
18
18
18
37
A
C
B
D
18
A × C - B × D
(Real Part)
Adder
36
36
18
18
37
A
D
B
C
A × D + B × C
(Imaginary Part)
18
18
18
DSP Block