FTCLEX

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

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

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

Inputs						Outputs
CLR	L	CE	T	D	C	Q
1	X	X	X	X	X	0
0	1	1	X	1		1
0	1	1	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 5.56 FTCLEX Implementation XC4000, XC5200, Spartans, Virtex