DESCRIPTION

The HEF4522B is a synchronous programmable 4-bit BCD down counter with an active HIGH and an active LOW clock input (CP0, CP1), an asynchronous parallel load input (PL), four parallel inputs (P0 to P3), a cascade feedback input (CF), four buffered parallel outputs (O0 to O3), a terminal count output (TC) and an overriding asynchronous master reset input (MR).

This device is a programmable, cascadable down counter with a decoded TC output for divide-by-n applications. In single stage applications the TC output is connected to PL. CF allows cascade divide-by-n operation with no additional gates required.

Information on P0 to P3 is loaded into the counter while PL is HIGH, independent of all other input conditions except MR, which must be LOW. When PL and CP1 are LOW, the counter advances on a LOW to HIGH transition of CP0. When PL is LOW and CP0 is HIGH, the counter advances on a HIGH to LOW transition of CP1. TC is HIGH when the counter is in the zero state (O0 = O1 = O2 = O3 = LOW) and CF is HIGH and PL is LOW. A HIGH on MR resets the counter (O0 to O3 = LOW) independent of other input conditions.

Schmitt-trigger action in the clock input makes the circuit highly tolerant to slower clock rise and fall times.