Xilinx CPLD Libraries Guide

About Design Elements
FDPE
Primitive: D Flip-Flop with Clock Enable and Asynchronous Preset
Supported Architectures
This design element is supported in the following architectures only:
• XC9500XL
• CoolRunner XPLA3
• CoolRunner-II
Introduction
This design element is a single D-type flip-flop with data (D), clock enable (CE), and asynchronous preset
(PRE) inputs and data output (Q). The asynchronous PRE, when High, overrides all other inputs and sets the
(Q) output High. Data on the (D) input is loaded into the flip-flop when PRE is Low and CE is High on the
Low-to-High clock (C) transition. When CE is Low, the clock transitions are ignored.
For CPLD devices, this flip-flop is asynchronously cleared, output Low, when power is applied. You can simulate
power-on by applying a High-level pulse on the PRLD global net.
Logic Table
Inputs Outputs
PRE CE D C Q
1 X X X 1
0 0 X X No Change
0 1 D › D
Design Entry Method
This design element is only for use in schematics.
Available Attributes
Attribute Type Allowed Values Default Description
INIT 1-Bit Binary 0 or 1 0 Sets the initial value
of Q output after
configuration
CPLD Libraries Guide
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