DM74LS191

DM54LS190 DM74LS190 DM54LS191 DM74LS191 Synchronous 4-Bit Up Down Counters with Mode Control May 1989 DM54LS190 DM74LS190 DM54LS191 DM74LS191 Synchronous 4-Bit Up Down Counters with Mode Control General Description These circuits are synchronous reversible up down counters The LS191 is a 4-bit binary counter and the LS190 is a BCD counter Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change simultaneously when so instructed by the steering logic This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple clock) counters The outputs of the four master-slave flip-flops are triggered on a low-to-high level transition of the clock input if the enable input is low A high at the enable input inhibits counting Level changes at either the enable input or the down up input should be made only when the clock input is high The direction of the count is determined by the level of the down up input When low the counter counts up and when high it counts down These counters are fully programmable that is the outputs may be preset to either level by placing a low on the load input and entering the desired data at the data inputs The output will change independent of the level of the clock input This feature allows the counters to be used as moduloN dividers by simply modifying the count length with the preset inputs The clock down up and load inputs are buffered to lower the drive requir...