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HD74LS191
Synchronous Up / Down 4-bit Binary Counter (single clock line)
REJ03D0453–0200 Rev.2.00
Feb.18.2005
Synchronous operation is provided by having all flip-flops clocked simultaneously so that 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 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. Level changes at the down / up input should be made only when the clock input is high.
HD74LS191 Datasheet
