FTCE

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

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

The flip-flop is asynchronously cleared, output Low, when power is applied. For CPLDs, the power-on condition can be simulated by applying a High-level pulse on the PRLD global net. FPGAs simulate power-on when global reset (GR) or global set/reset (GSR) is active. GR for XC3000 is active-Low. 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, STARTUP_SPARTAN2, or STARTUP_VIRTEX symbol.

Inputs				Outputs
CLR	CE	T	C	Q
1	X	X	X	0
0	0	X	X	No Chg
0	1	0	X	No Chg
0	1	1		Toggle

Figure 5.51 FTCE Implementation XC3000, XC4000E, XC4000X, XC5200, Spartan, SpartanXL, Spartan2, Virtex

Figure 5.52 FTCE Implementation XC9000