LDCPE_1

Transparent Data Latch with Asynchronous Clear and Preset, Gate Enable, and Inverted Gate

LDCPE_1 is a transparent data latch with data (D), asynchronous clear (CLR), asynchronous preset (PRE), and gate enable (GE). When CLR is High, it overrides the other inputs and resets the data (Q) output Low. When PRE is High and CLR is Low, it presets the data (Q) output High. Q reflects the data (D) input while gate enable (GE) is High and gate (G), CLR, and PRE are Low. The data on the D input during the Low-to-High gate transition is stored in the latch. The data on the Q output remains unchanged as long as G is High or GE is Low.

The latch is asynchronously cleared, output Low, when power is applied. Virtex and Spartan2 simulate 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_SPARTAN2 or STARTUP_VIRTEX symbol.

Inputs					Outputs
CLR	PRE	GE	G	D	Q
1	X	X	X	X	0
0	1	X	X	X	1
0	0	0	X	X	No Chg
0	0	1	0	0	0
0	0	1	0	1	1
0	0	1	1	X	No Chg
0	0	1		D	d
d = state of input one setup time prior to Low-to-High gate transition