EP2S180F1020C4 Datasheet, PDF (537/768 Pages) Altera Corporation – Stratix II Device Handbook, Volume 1

Operational
Modes
DSP Blocks in Stratix II and Stratix II GX Devices
The DSP block can be used in one of four basic operational modes, or a
combination of two modes, depending on the application needs.
Table 6–7 shows the four basic operational modes and the number of
multipliers that can be implemented within a single DSP block
depending on the mode.
Table 6–7. DSP Block Operational Modes
Mode
Simple multiplier
Multiply
accumulate
Two-multiplier
adder
Four-multiplier
adder
Number of Multipliers
9×9
18 × 18
36 × 36
Eight multipliers Four multipliers
with eight product with four product
outputs
outputs
One multiplier
-
Two 52-bit
-
multiply-
accumulate blocks
Four two-multiplier Two two-multiplier
-
adder (two 9 × 9 adder (one
complex multiply) 18 × 18 complex
multiply)
Two four-multiplier One four-multiplier
-
adder
adder
The Quartus II software includes megafunctions used to control the mode
of operation of the multipliers. After you make the appropriate parameter
settings using the megafunction’s MegaWizard^® Plug-In Manager, the
Quartus II software automatically configures the DSP block.
Stratix II and Stratix II GX DSP blocks can operate in different modes
simultaneously. For example, a single DSP block can be broken down to
operate a 9 × 9 multiplier as well as an 18 × 18 multiplier-adder where
both multiplier's input a and input b have the same sign representations.
This increases DSP block resource efficiency and allows you to implement
more multipliers within a Stratix II or Stratix II GX device. The Quartus II
software automatically places multipliers that can share the same DSP
block resources within the same block.
Additionally, you can set up each Stratix II or Stratix II GX DSP block to
dynamically switch between the following three modes:
■ Up to four 18-bit independent multipliers
■ Up to two 18-bit multiplier-accumulators
■ One 36-bit multiplier
Altera Corporation
January 2008
6–21
Stratix II Device Handbook, Volume 2