HD74HC669

HD74HC668, HD74HC669 Synchronous UP/Down Decade Counter Synchronous Up/Down 4-bit binary Counter REJ03D0638-0200 (Previous ADE-205-520) Rev.2.00 Mar 30, 2006 Description This synchronous presettable decade counter features an internal carry look-ahead 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 inputs and internal gating. This mode of operation helps eliminate the output counting spikes that are normally associated with asynchronous (ripple-clock) counters. A buffered clock input triggers the four master-slave flip-flops on the rising (positive going) edge of the clock waveform. This counter is fully programmable; that is, the outputs may each be preset to either level. The load input circuitry allows loading with the carry-enable output of cascaded counters. As loading is synchronous, setting up a low leve...