SL74HC161

System Logic

Semiconductor

SLS

GND=Pin 8

The flip-flops shown in the circuit diagrams are Toggle-Enable flip-flops. A Toggle-Enable flip-flop is a

combination of a D flip-flop and a T flip-flop. When loading data from Preset inputs P0, P1, P2, and P3, the Load

signal is used to disable the Toggle input (Tn) of the flip-flop. The logic level at the Pn input is then clocked to

the Q output of the flip-flop on the next rising edge of the clock.

A logic zero on the Reset device input forces the internal clock (C) high and resets the Q output of the flip-

flop low.

Figure 7.Expanded logic diagram