FDCP

D Flip-Flop Asynchronous Preset and Clear

FDCP is a single D-type flip-flop with data (D), asynchronous preset (PRE) and clear (CLR) inputs, and data output (Q). The asynchronous PRE, when High, sets the Q output High; CLR, when High, resets the output Low. Data on the D input is loaded into the flip-flop when PRE and CLR are Low on the Low-to-High clock (C) 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. Virtex simulates power-on when global set/reset (GSR) is active. GSR defaults to active-High but can be inverted by adding an inverter in front of the GSR input of the STARTUP_VIRTEX symbol.

Inputs				Outputs
CLR	PRE	D	C	Q
1	X	X	X	0
0	1	X	X	1
0	0	0		0
0	0	1		1