5

ATF1508ASV(L)

1408H–PLD–7/05

Flip-flop

The ATF1508ASV(L)’s flip-flop has very flexible data and control functions. The data

input can come from either the XOR gate, from a separate product term or directly from

the I/O pin. Selecting the separate product term allows creation of a buried registered

feedback within a combinatorial output macrocell. (This feature is automatically imple-

mented by the fitter software). In addition to D, T, JK and SR operation, the flip-flop can

also be configured as a flow-through latch. In this mode, data passes through when the

clock is high and is latched when the clock is low.

The clock itself can either be the Global CLK Signal (GCK) or an individual product term.

The flip-flop changes state on the clock's rising edge. When the GCK signal is used as

the clock, one of the macrocell product terms can be selected as a clock enable. When

the clock enable function is active and the enable signal (product term) is low, all clock

edges are ignored. The flip-flop’s asynchronous reset signal (AR) can be either the Glo-

bal Clear (GCLEAR), a product term, or always off. AR can also be a logic OR of

GCLEAR with a product term. The asynchronous preset (AP) can be a product term or

always off.

Figure 1. ATF1508ASV(L) Macrocell