FTPLE

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

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 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 or the 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 XC4000, XC5200, Spartans, Virtex

Figure 5.64 FTPLE Implementation XC9000