— OBSOLETE — OBSOLETE — OBSOLETE — OBSOLETE —
R
Virtex-II Platform FPGAs: Functional Description
Each SelectRAM memory and multiplier block is tied to four
switch matrices, as shown in Figure 35.
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 36 shows a multiplier block.
Switch
Matrix
Multiplier Block
A[17:0]
Switch
Matrix
MULT 18 x 18
P[35:0]
18-Kbit block
SelectRAM
B[17:0]
Switch
Matrix
DS031_40_100400
Figure 36: Multiplier Block
Switch
Matrix
Locations / Organization
Multiplier organization is identical to the 18 Kbit SelectRAM
organization, because each multiplier is associated with an
18 Kbit block SelectRAM resource.
DS031_33_101000
Figure 35: SelectRAM and Multiplier Blocks
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)).
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 multi-
plier shares inputs with the upper data bits of the
SelectRAM memory.
Table 20: Multiplier Floor Plan
Multipliers
Device
Columns
Per Column
Total
4
XC2V40
2
2
4
4
4
4
4
6
6
6
6
2
This sharing of the interconnect is optimized for an
18-bit-wide block SelectRAM resource feeding the multi-
plier. The use of SelectRAM memory and the multiplier with
an accumulator in LUTs allows for implementation of a digi-
tal signal processor (DSP) multiplier-accumulator (MAC)
function, which is commonly used in finite and infinite
impulse response (FIR and IIR) digital filters.
XC2V80
4
8
XC2V250
XC2V500
XC2V1000
XC2V1500
XC2V2000
XC2V3000
XC2V4000
XC2V6000
XC2V8000
6
24
8
32
10
12
14
16
20
24
28
40
48
56
96
120
144
168
DS031-2 (v4.0) April 7, 2014
Product Specification
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