R
Virtex™-II Platform FPGAs: Detailed Description
Total Amount of SelectRAM Memory
Table 18 shows the amount of block SelectRAM memory
available for each Virtex-II device. The 18 Kbit SelectRAM
blocks are cascadable to implement deeper or wider single- or
dual-port memory resources.
Switch
Matrix
Table 18: Virtex-II SelectRAM Memory Available
Switch
Matrix
Total SelectRAM Memory
18-Kbit block
SelectRAM
Device
Blocks
4
in Kbits
72
in Bits
73,728
Switch
Matrix
XC2V40
XC2V80
8
144
147,456
442,368
589,824
737,280
884,736
1,032,192
1,769,472
2,211,840
2,654,208
3,096,576
XC2V250
XC2V500
XC2V1000
XC2V1500
XC2V2000
XC2V3000
XC2V4000
XC2V6000
XC2V8000
24
432
Switch
Matrix
32
576
40
720
DS031_33_101000
48
864
Figure 35: SelectRAM and Multiplier Blocks
56
1,008
1,728
2,160
2,592
3,024
Association With Block SelectRAM Memory
96
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.
120
144
168
18-Bit x 18-Bit Multipliers
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.
Introduction
A Virtex-II multiplier block is an 18-bit by 18-bit 2’s comple-
ment signed multiplier. Virtex-II devices incorporate many
embedded multiplier blocks. These multipliers can be asso-
ciated 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.
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.
Each SelectRAM memory and multiplier block is tied to four
switch matrices, as shown in Figure 35.
Multiplier Block
A[17:0]
MULT 18 x 18
P[35:0]
B[17:0]
DS031_40_100400
Figure 36: Multiplier Block
DS031-2 (v3.0) August 1, 2003
Product Specification
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