The 74HC/HCT74 is a high-speed Si-gate CMOS device
and is pin compatible with low power Schottky TTL
(LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The 74HC/HCT74 are dual positive-edge triggered, D-type
flip-flops with individual data (D) inputs, clock (CP) inputs,
set (SD) and reset (RD) inputs; also complementary
Q and Q outputs.
The set and reset are asynchronous active LOW inputs
and operate independently of the clock input. Information
on the data input is transferred to the Q output on the
LOW-to-HIGH transition of the clock pulse. The D inputs
must be stable one set-up time prior to the LOW-to-HIGH
clock transition for predictable operation.
Schmitt-trigger action in the clock input makes the circuit
highly tolerant to slower clock rise and fall times.