Libraries GuideChapter 5: Design Elements (F5MAP to FTSRLE)
FDSE_1
D Flip-Flop with Negative-Edge Clock, Clock Enable, and Synchronous Set
XC3000
| XC4000E
| XC4000X
| XC5200
| XC9000
| Spartan
| SpartanXL
| Spartan2
| Virtex
|
|---|
N/A
| N/A
| N/A
| N/A
| N/A
| N/A
| N/A
| Primitive
| Primitive
|
FDSE_1 is a single D-type flip-flop with data (D), clock enable (CE), and synchronous set (S) inputs and data output (Q). The synchronous set (S) input, when High, overrides the clock enable (CE) input and sets the Q output High during the High-to-Low clock (C) transition. The data on the D input is loaded into the flip-flop when S is Low and CE is High during the High-to-Low clock (C) transition.
For Virtex and Spartan2, the flip-flop is asynchronously preset, output High, when power is applied. Virtex and Spartan2 simulate power-on when global set/reset (GSR) is active. GSR defaults to active-High but can be inverted by adding an inverter in front of the GSR input of the STARTUP_SPARTAN2 or STARTUP_VIRTEX symbol.
Inputs
| Outputs
|
|---|
S
| CE
| D
| C
| Q
|
|---|
1
| X
| X
| 
| 1
|
0
| 0
| X
| X
| No Chg
|
0
| 1
| 1
|
| 1
|
0
| 1
| 0
|
| 0
|
