XC2VP4 XILINX [Xilinx, Inc], XC2VP4 Datasheet - Page 50

• Manufacturer Part Number: XC2VP4
• Description: Virtex-II Pro and Virtex-II Pro X Platform FPGAs
• Manufacturer: XILINX [Xilinx, Inc]

Shift Registers
Each function generator can also be configured as a 16-bit
shift register. The write operation is synchronous with a
clock input (CLK) and an optional clock enable, as shown in
Figure
4-bit address bus, A[3:0]. The configurable 16-bit shift regis-
ter cannot be set or reset. The read is asynchronous; how-
ever, the storage element or flip-flop is available to
implement a synchronous read. Any of the 16 bits can be
read out asynchronously by varying the address. The stor-
age element should always be used with a constant
address. For example, when building an 8-bit shift register
and configuring the addresses to point to the 7th bit, the 8th
bit can be the flip-flop. The overall system performance is
improved by using the superior clock-to-out of the flip-flops.
An additional dedicated connection between shift registers
allows connecting the last bit of one shift register to the first
bit of the next, without using the ordinary LUT output. (See
Figure
access to any bit in the chain. The shift register chaining
and the MUXF5, MUXF6, and MUXF7 multiplexers allow up
to a 128-bit shift register with addressable access to be
implemented in one CLB.
DS083 (v4.7) November 5, 2007
Product Specification
CE (SR)
D(BY)
A[3:0]
SHIFTIN
CLK
39. A dynamic read access is performed through the
40.) Longer shift registers can be built with dynamic
Figure 39: Shift Register Configurations
R
4
WE
CK
A[4:1]
WS
SRLC16
WSG
SHIFT-REG
MC15
DI
D
SHIFTOUT
(optional)
D
Q
Virtex-II Pro and Virtex-II Pro X Platform FPGAs: Functional Description
DS031_05_110600
Output
Registered
Output
www.xilinx.com
1 Shift Chain
in CLB
SRLC16
SRLC16
SRLC16
SRLC16
Figure 40: Cascadable Shift Register
DI
DI
DI
DI
MC15
MC15
MC15
MC15
SHIFTIN
SHIFTIN
D
D
D
D
SLICE S3
SLICE S2
IN
SHIFTOUT
OUT
FF
FF
FF
FF
CASCADABLE OUT
SLICE S1
SLICE S0
DI
SRLC16
SRLC16
SRLC16
SRLC16
DI
DI
SHIFTIN
DI
MC15
MC15
MC15
MC15
D
D
D
D
SHIFTOUT
SHIFTOUT
DS031_06_110200
FF
FF
FF
FF
Module 2 of 4
CLB
39