The Harris CD74HC4518 is a dual BCD up-counter. The Harris CD74HC4520 and CD74HCT4520 are dual binary up-counters. Each device consists of two independent internally synchronous 4-stage counters. The counter stages are D-type flip-flops having interchangeable CLOCK and ENABLE lines for incrementing on either the positive-going or the negative-going transition of CLOCK. The counters are cleared by high levels on the MASTER RESET lines. The counter can be cascaded in the ripple mode by connecting Q3 to the ENABLE input of the subsequent counter while the CLOCK input of the latter is held low.