Digital Signal Processing Block
Output Selection Multiplexer
The outputs from the various elements of the adder/output block are
routed through an output selection multiplexer. Based on the DSP block
operational mode and user settings, the multiplexer selects whether the
output from the multiplier, the adder/subtractor/accumulator, or
summation block feeds to the output.
Output Registers
Optional output registers for the DSP block outputs are controlled by four
sets of control signals: clock[3..0], aclr[3..0], and ena[3..0].
Output registers can be used in any mode.
Modes of Operation
The adder, subtractor, and accumulate functions of a DSP block have four
modes of operation:
■
■
■
■
Simple multiplier
Multiply-accumulator
Two-multipliers adder
Four-multipliers adder
1
Each DSP block can only support one mode. Mixed modes in the
same DSP block is not supported.
Simple Multiplier Mode
In simple multiplier mode, the DSP block drives the multiplier sub-block
result directly to the output with or without an output register. Up to four
18 × 18-bit multipliers or eight 9 × 9-bit multipliers can drive their results
directly out of one DSP block. See Figure 2–35.
2–64
Stratix Device Handbook, Volume 1
Altera Corporation
July 2005
ALTERA [ ALTERA CORPORATION ]
