XQ2V1000_1 Datasheet, PDF (33/134 Pages) Xilinx, Inc – QPro Virtex-II 1.5V Platform FPGAs

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QPro Virtex-II 1.5V Platform FPGAs
18-Bit x 18-Bit Multipliers
Introduction
A Virtex-II multiplier block is an 18-bit by 18-bit 2’s
complement signed multiplier. Virtex-II devices incorporate
many embedded multiplier blocks. These multipliers can be
associated with an 18 Kbit block SelectRAM resource or
can be used independently. They are optimized for high-
speed operations and have a lower power consumption
compared to an 18-bit x 18-bit multiplier in slices.
Each SelectRAM memory and multiplier block is tied to four
switch matrices, as shown in Figure 36.
X-Ref Target - Figure 36
Switch
Matrix
Switch
Matrix
Switch
Matrix
18-Kbit block
SelectRAM
Switch
Matrix
DS031_33_101000
Figure 36: SelectRAM and Multiplier Blocks
Association with Block SelectRAM Memory
The interconnect is designed to allow SelectRAM memory
and multiplier blocks to be used at the same time, but some
interconnect is shared between the SelectRAM and the
multiplier. Thus, SelectRAM memory can be used only up to
18 bits wide when the multiplier is used, because the
multiplier shares inputs with the upper data bits of the
SelectRAM memory.
This sharing of the interconnect is optimized for an 18-bit-
wide block SelectRAM resource feeding the multiplier. The
use of SelectRAM memory and the multiplier with an
accumulator in LUTs allows for implementation of a digital
signal processor (DSP) multiplier-accumulator (MAC)
function, which is commonly used in finite and infinite
impulse response (FIR and IIR) digital filters.
Configuration
The multiplier block is an 18-bit by 18-bit signed multiplier
(2's complement). Both A and B are 18-bit-wide inputs, and
the output is 36 bits. Figure 37 shows a multiplier block.
X-Ref Target - Figure 37
Multiplier Block
A[17:0]
B[17:0]
MULT 18 x 18
P[35:0]
DS031_40_100400
Figure 37: Multiplier Block
Locations/Organization
Multiplier organization is identical to the 18 Kbit SelectRAM
organization, because each multiplier is associated with an
18 Kbit block SelectRAM resource.
In addition to the built-in multiplier blocks, the CLB elements
have dedicated logic to implement efficient multipliers in
logic (refer to "Configurable Logic Blocks (CLBs)," page 19).
Table 24: Multiplier Floor Plan
Device
Columns
Multipliers
Per Column
Total
XQ2V1000
4
10
40
XQ2V3000
6
16
96
XQ2V6000
6
24
144
DS122 (v2.0) December 21, 2007
www.xilinx.com
Product Specification
33