General Description

Each of these monolithic counters contains four masterslave

flip-flops and additional gating to provide a divide-bytwo

counter and a three-stage binary counter for which the

count cycle length is divide-by-five for the DM74LS90.

All of these counters have a gated zero reset and the

DM74LS90 also has gated set-to-nine inputs for use in

BCD nine’s complement applications.

To use their maximum count length (decade or four bit

binary), the B input is connected to the QA output. The

input count pulses are applied to input A and the outputs

are as described in the appropriate truth table. A symmetrical

divide-by-ten count can be obtained from the

DM74LS90 counters by connecting the QD output to the A

input and applying the input count to the B input which

gives a divide-by-ten square wave at output QA.

Features

n Typical power dissipation 45 mW

n Count frequency 42 MHz