The UT54ACS163 and the UT54ACTS163 are synchronous presettable 4-bit binary counters that feature internal carry lookahead logic for high-speed counting designs. Synchronous operation occurs by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when instructed by the count-enable inputs and internal gating. A buffered clock input triggers the four flip-flops on the rising (positive-going) edge of the clock input waveform. The counters are fully programmable (i.e., they may be preset to any number between 0 and 15). Presetting is synchronous; applying a low level at the load input disables the counter and causes the outputs to agree with the load data after the next clock pulse.