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FTC

Toggle Flip-Flop with Toggle Enable and Asynchronous Clear

XC3000
XC4000E
XC4000X
XC5200
XC9000
Spartan
SpartanXL
Virtex
Macro
Macro
Macro
Macro
Macro
Macro
Macro
Macro

figures/x3761n.gif

FTC is a synchronous, resettable toggle flip-flop. The asynchronous clear (CLR) input, when High, overrides all other inputs and resets the data output (Q) Low. The Q output toggles, or changes state, when the toggle enable (T) input is High and CLR is Low during the Low-to-High clock transition.

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 or STARTUP_VIRTEX symbol.

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

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Figure 5.49 FTC Implementation XC3000, XC4000, XC5200, Spartans, Virtex

Figure 5.50 FTC Implementation XC9000

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