파트넘버 : 74LS190
기능 : Synchronous Up/Down Decade Counters(single clock line)
제조사 : Hitachi Semiconductor
Synchronous 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.
The outputs of the four master-slave flip-flops are triggered on a low-to-high-level transition of the clock input if the enable input is low. A high at the enable input inhibits counting. Level changes at the enable input should be made only when the clock input is high. The direction of the count is determined by the level of the down / up input. When low, the counter counts up and when high, it counts down.