CD74HCT123E

The ?HC123, ?HCT123, CD74HC423 and CD74HCT423 are
dual monostable multivibrators with resets. They are all
retriggerable and differ only in that the 123 types can be
triggered by a negative to positive reset pulse; whereas the
423 types do not have this feature. An external resistor (RX)
and an external capacitor (CX) control the timing and the
accuracy for the circuit. Adjustment of Rx and CX provides a
wide range of output pulse widths from the Q and Q
terminals. Pulse triggering on the A and B inputs occur at a
particular voltage level and is not related to the rise and fall
times of the trigger pulses.
Once triggered, the output pulse width may be extended by
retriggering inputs A and B. The output pulse can be
terminated by a LOW level on the Reset (R) pin. Trailing
edge triggering (A) and leading edge triggering (B) inputs
are provided for triggering from either edge of the input
pulse. If either Mono is not used each input on the unused
device (A, B, and R) must be terminated high or low