The CD74HCT123M is a dual Monostable Multivibrator with RESETs. It is a 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.
Description 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.
The 74HCT123D is a dual retriggerable Monostable Multivibrator with a reset. It is pin compatible with low-power Schottky TTL (LSTTL). It comes with an output pulse width control. The Schmitt-trigger action in the nA and nB inputs, makes the circuit highly tolerant to slower input rise and fall times. The output pulse is controlled by three methods, first - The basic pulse is programmed by selection of an external resistor (REXT) and capacitor (CEXT). Second, once triggered, the basic output pulse width may be extended by retriggering the gated active low-going edge input (nA\\) or the active high-going edge input (nB). By repeating this process, the output pulse period (nQ = high, nQ\ = low) can be made as long as desired. Alternatively an output delay can be terminated at any time by a low-going edge on input nRD\, which also inhibits the triggering. Third, an internal connection from nRD to the input gates makes it possible to trigger.