Tuesday, July 6, 2010

Decade Counter

The 7490A monolithic counter contains four masterslave flip-flops and additional gating to provide a divide-by two counter and a three-stage binary counter for which the count cycle length is divide-by-five. The counter has a gated zero reset and also has gated setto- nine inputs for use in BCD nine’s complement applications.

To use the 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 Function Table. A symmetrical divide-by-ten count can be obtained from the counters by connecting the QD output to the A input and applying the input count to the B input which gives a divideby- ten square wave at output QA.

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