SN74F169DR [Texas Instruments]

This synchronous, presettable, 4-bit up/down binary counter features an internal carry look-ahead circuitry for cascading in high-speed counting applications. Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when so instructed by the count-enable (ENP, ENT) inputs and internal gating. This mode of operation eliminates the output counting spikes that are normally associated with asynchronous (ripple-clock) counters. A buffered clock (CLK) input triggers the four flip-flops on the rising (positive-going) edge of the clock waveform. This counter is fully programmable; that is, it may be preset to any number between 0 and its maximum count. The load-input circuitry allows loading with the carry-enable output of cascaded counters. As loading is synchronous, setting up a low level at the load (LOAD) input disables the counter and causes the outputs to agree with the data inputs after the next clock pulse. The carry look-ahead circuitry provides for cascading counters for n-bit synchronous application without additional gating. Instrumental in accomplishing this function are two count-enable (ENP, ENT) inputs and a ripple-carry (RCO) output. The SN74F169 features a fully independent clock circuit. The SN74F169 is characterized for operation from 0°C to 70°C.