DESCRIPTION
The 74ALS74 is a dual positive edge-triggered D-type flip-flop featuring individual data, clock, set, and reset inputs; also true and complementary outputs. Set (SD) and reset (RD) are asynchronous active-Low inputs and operate independently of the clock input.
When set and reset are inactive (High), data at the D input is transferred to the Q and Q outputs on the Low-to-High transition of the clock. Data must be stable just one setup time prior to the  Low-to-High transition of the clock for predictable operation. Clock triggering occurs at a voltage level and is not directly related to the transition time of the positive-going pulse. Following the hold time interval, data at the D input may be changed without affecting the levels of the output.