HD74HC191中文资料日立数据手册PDF规格书

The HD74HC190 and HD74HC191 are synchronous, reverside up/down counters. The HD74HC190 is a 4-bit decade counter and the HD74HC191 is a 4-bit binary counter. Synchronous counting operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when so instructed by the steering logic. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple clock) counters.