74HC74HC

The 74HC74HC is 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 74HC74HC is 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 of the 74HC74HC permits the counter to be preset to any desired number. Information of the 74HC74HC 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. As indicated in the function table, this operation overrides the counting function.

Counting of the 74HC74HC 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 as indicated in the function table. 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. Also, the U/D input should be changed only when either CE or CP is HIGH.