xc2vp2 Xilinx Corp., xc2vp2 Datasheet - Page 37

• Manufacturer Part Number: xc2vp2
• Description: Virtex-ii Pro And Virtex-ii Pro X Platform Fpgas
• Manufacturer: Xilinx Corp.

This DDR mechanism can be used to mirror a copy of the
clock on the output. This is useful for propagating a clock
along the data that has an identical delay. It is also useful for
multiple clock generation, where there is a unique clock
driver for every clock load. Virtex-II Pro devices can pro-
duce many copies of a clock with very little skew.
Each group of two registers has a clock enable signal (ICE
for the input registers, OCE for the output registers, and
TCE for the 3-state registers). The clock enable signals are
active High by default. If left unconnected, the clock enable
for that storage element defaults to the active state.
Each IOB block has common synchronous or asynchronous
set and reset (SR and REV signals). Two neighboring IOBs
have a shared routing resource connecting the ICLK and
OTCLK pins on pairs of IOBs. If two adjacent IOBs using
DDR registers do not share the same clock signals on their
clock pins (ICLK1, ICLK2, OTCLK1, and OTCLK2), one of
the clock signals will be unroutable.
The IOB pairing is identical to the LVDS IOB pairs. Hence,
the package pin-out table can also be used for pin assign-
ment to avoid conflict.
SR forces the storage element into the state specified by the
SRHIGH or SRLOW attribute. SRHIGH forces a logic 1.
SRLOW forces a logic “0”. When SR is used, a second input
DS083 (v4.7) November 5, 2007
Product Specification
R
DCM
0°
D1
D2
CLK1
CLK2
Q1
Q2
Figure 20: Double Data Rate Registers
DDR MUX
Virtex-II Pro and Virtex-II Pro X Platform FPGAs: Functional Description
FDDR
www.xilinx.com
Q
(REV) forces the storage element into the opposite state. The
reset condition predominates over the set condition. The ini-
tial state after configuration or global initialization state is
defined by a separate INIT0 and INIT1 attribute. By default,
the SRLOW attribute forces INIT0, and the SRHIGH attribute
forces INIT1.
For each storage element, the SRHIGH, SRLOW, INIT0,
and INIT1 attributes are independent. Synchronous or
asynchronous set / reset is consistent in an IOB block.
All the control signals have independent polarity. Any
inverter placed on a control input is automatically absorbed.
Each register or latch, independent of all other registers or
latches, can be configured as follows:
•
•
•
•
•
•
•
The synchronous reset overrides a set, and an asynchro-
nous clear overrides a preset.
Refer to
180° 0°
DCM
No set or reset
Synchronous set
Synchronous reset
Synchronous set and reset
Asynchronous set (preset)
Asynchronous reset (clear)
Asynchronous set and reset (preset and clear)
Figure
21.
D1
D2
CLK1
CLK2
Q1
Q2
DDR MUX
FDDR
DS083-2_26_122001
Q
Module 2 of 4
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