EP2S90F1020C5 Datasheet, PDF (538/768 Pages) Altera Corporation – Stratix II Device Handbook, Volume 1

Operational Modes
Each half of a Stratix II or Stratix II GX DSP block has separate mode
control signals, which allows you to implement multiple 18-bit
multipliers or multiplier-accumulators within the same DSP block and
dynamically switch them independently (if they are in separate DSP
block halves). If the design requires a 36-bit multiplier, you must switch
the entire DSP block to accommodate the it since the multiplier requires
the entire DSP block. The smallest input bit width that supports dynamic
mode switching is 18 bits.
Simple Multiplier Mode
In simple multiplier mode, the DSP block performs individual
multiplication operations for general-purpose multipliers and for
applications such as computing equalizer coefficient updates which
require many individual multiplication operations.
9- and 18-Bit Multipliers
Each DSP block multiplier can be configured for 9- or 18-bit
multiplication. A single DSP block can support up to eight individual
9 × 9 multipliers or up to four individual 18 × 18 multipliers. For operand
widths up to 9-bits, a 9 × 9 multiplier will be implemented and for
operand widths from 10- to 18-bits, an 18 × 18 multiplier will be
implemented. Figure 6–8 shows the DSP block in the simple multiplier
operation mode.
6–22
Stratix II Device Handbook, Volume 2
Altera Corporation
January 2008