SN74LS390N .

产品概述

The SN74LS390N is a 4bit dual decade counter contains eight flip-flops and additional gating to implement two individual four-bit counters. It incorporates dual divide-by-two and divide-by-five counter, which can be used to implement cycle lengths equal to any whole and/or cumulative multiples of 2 and/or 5 up to divide-by-100. When connected as a bi-quinary counter, the separate divide-by-two circuit can be used to provide symmetry (a square wave) at the final output stage. It comprises two independent four-bit binary counters each having a clear and a clock input. N-bit binary counters can be implemented with each package providing the capability of divide-by-256. It has parallel outputs from each counter stage so that any submultiple of the input count frequency is available for system-timing signals.

• Direct clear for each 4bit counter
• Buffered outputs reduce possibility of collector commutation