The CD74AC191 and CD74ACT191 are asynchronously presettable binary up/down synchronous counters that utilize the Harris Advanced CMOS Logic technology. Presetting the counter to the number on preset data inputs (P0-P3) is accomplished by setting LOW the asynchronous parallel load input (PL). Counting occurs when PL is HIGH, Count Enable (CE) is LOW, and the Up/Down (U/D) input is either LOW for up-counting or HIGH for down-counting. The counter is incremented or decremented synchronously with the LOW-to-HIGH transition of the clock.