74HC191N

The 74HC191N is a presettable synchronous 4bit binary up/down counter, pin compatible with low power schottky TTL (LSTTL). It is asynchronously presettable 4bit binary up/down counters. They contain four flip-flops with internal gating and steering logic to provide asynchronous preset and synchronous count-up and count-down operation. Asynchronous parallel load capability permits the counter to be preset to any desired number. Information present on the parallel data inputs (D0 to D3) is loaded into the counter and appears on the outputs when the parallel load (PL\) input is low. Counting is inhibited by a HIGH level on the count enable (CE\) input. When CE\ is low internal state changes are initiated synchronously by the low-to-high transition of the clock input. The up/down (U\/D) input signal determines the direction of counting. The CE input may go low when the clock is in either state, however, the low-to-high CE\ transition must occur only when the clock is high.

• Synchronous reversible counting
• Count enable control for synchronous expansion
• Single up/down control input
• Standard output capability
• ICC category