DM74LS74AN Datasheet PDF - Fairchild

●General Description

●This device contains two independent positive-edge-triggered D flip-flops with complementary outputs. The information on the D input is accepted by the flip-flops on the positive going edge of the clock pulse. The triggering occurs at a voltage level and is not directly related to the transition time of the rising edge of the clock.  The data on the D input may be changed while the clock is LOW or HIGH without affecting the outputs as long as the data setup and hold times are not violated. A low logic level on  the preset or clear inputs will set or reset the outputsregardless of the logic levels of the other inputs.