The M54/74HC221/221A are high speed CMOS MONOSTABLE multivibrators fabricated with silicon gate C2MOS technology. It achieves the high speed operation similar to equivalent LSTTL while maintaining the CMOS low power dissipation. There are two trigger inputs, A INPUT (negative edge) and B INPUT (positive edge). Triggering on the B input occurs at a particular voltage threshold and is not related to the rise and fall time of the applied pulse. The device may also be triggered by using the CLR input (positive-edge) because of the Schmitt-trigger input ; after triggering the output maintains the MONOSTABLEstate for the time period determined by the external resistor Rx and capacitor Cx.Taking CLR low breaks this MONOSTABLE STATE. If the next trigger pulse occurs during the MONOSTABLE period it makes the MONOSTABLE period longer. Limit for values of Cx and Rx : Cx : NO LIMIT