The M74HC191 is a high speed CMOS 4-bit synchronous up/down counter fabricated with silicon gate C2MOS technology. State changes of the counter are synchronous with the LOW-to-HIGH transition of the Clock Pulse Input. An asynchronous parallel load input overrides counting and loads the data present on the DATA inputs into the flip-flops, which makes it possible to use the circuits as programmable counters. A count enable input serves as the carry/borrow input in multi-stage counters. Control input, Down/ Up, determines whether a circuit counts up or down. A MAX/MIN output and a Ripple Clock output provide overflow/underflow indication and make possible a variety of methods for generating carry/borrow signals in multi-stage counter applications. All inputs are equipped with protection circuits against static discharge and transient excess voltage.