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DUAL DECADE COUNTER; DUAL 4-STAGE BINARY COUNTER
The SN54 / 74LS390 and SN54 / 74LS393 each contain a pair of high-speed 4-stage ripple counters. Each half of the LS390 is partitioned into a divide-by-two section and a divide-by five section, with a separate clock input for each section. The two sections can be connected to count in the 8.4.2.1 BCD code or they can count in a biquinary sequence to provide a square wave (50% duty cycle) at the final output. Each half of the LS393 operates as a Modulo-16 binary divider, with the last three stages triggered in a ripple fashion. In both the LS390 and the LS393, the flip-flops are triggered by a HIGH-to-LOW transition of their CP inputs.
SN54LS390 Datasheet
