Description
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
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