74HC191D,653

The 74HC/HCT191 are high-speed Si-gate CMOS devices and are pin compatible with low power Schottky TTL (LSTTL). They are specified in compliance with JEDEC standard no. 7A. The 74HC/HCT191 are asynchronously presettable 4-bit binary up/down counters. They contain four master/slave 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 input is LOW. As indicated in the function table, this operation overrides the counting function.