XC2VP70 Xilinx, Inc., XC2VP70 Datasheet - Page 37

• Manufacturer Part Number: XC2VP70
• Description: Virtex-ii Pro Field Programmable Gate Array
• Manufacturer: Xilinx, Inc.

Functional Description: FPGA
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.
28
CE (SR)
D(BY)
A[3:0]
SHIFTIN
CLK
30. A dynamic read access is performed through the
31.) Longer shift registers can be built with dynamic
Figure 30: Shift Register Configurations
4
WE
CK
A[4:1]
WS
SRLC16
WSG
SHIFT-REG
MC15
DI
D
SHIFTOUT
(optional)
D
Q
DS031_05_110600
Output
Registered
Output
www.xilinx.com
1-800-255-7778
1 Shift Chain
in CLB
SRLC16
SRLC16
SRLC16
SRLC16
Figure 31: 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
DS083-2 (v2.9) October 14, 2003
Advance Product Specification
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
CLB
R