Return to previous page Advance to next page
Libraries Guide
Chapter 5: Design Elements (F5MAP to FTSRLE)

FTPLE

Toggle/Loadable Flip-Flop with Toggle and Clock Enable and Asynchronous Preset

XC3000
XC4000E
XC4000X
XC5200
XC9000
Spartan
SpartanXL
Spartan2
Virtex
N/A
Macro
Macro
Macro
Macro
Macro
Macro
Macro
Macro

FTPLE is a toggle/loadable flip-flop with toggle and clock enable and asynchronous preset. When the asynchronous preset input (PRE) is High, all other inputs are ignored and output Q is set High. When the load enable input (L) is High and PRE is Low, the clock enable (CE) is overridden and the data (D) is loaded into the flip-flop during the Low-to-High clock transition. When L and PRE are Low and toggle-enable input (T) and CE are High, output Q toggles, or changes state, during the Low-to-High clock transition. When CE is Low, clock transitions are ignored.

For FPGAs, the flip-flop is asynchronously preset to output High, when power is applied. FPGAs simulate power-on when global reset (GR for XC5200) or global set/reset (GSR for XC4000, Spartans, Virtex) is active. The GR/GSR active level defaults to active-High but can be inverted by adding an inverter in front of the GR/GSR input of the STARTUP, STARTUP_SPARTAN2, or STARTUP_VIRTEX symbol.

For CPLDs, the flip-flop is asynchronously cleared, output Low, when power is applied. The power-on condition can be simulated by applying a High-level pulse on the PRLD global net.

Inputs
Outputs
PRE
L
CE
T
D
C
Q
1
X
X
X
X
X
1
0
1
X
X
1

1
0
1
X
X
0

0
0
0
0
X
X
X
No Chg
0
0
1
0
X
X
No Chg
0
0
1
1
X

Toggle

Figure 5.63 FTPLE Implementation XC4000E, XC4000X, XC5200, Spartan, SpartanXL, Spartan2, Virtex

Figure 5.64 FTPLE Implementation XC9000