Mura The counters can be. When Dtasheet, the counter counts up. Do you already have an account? The output will change independent of the level of the clock input. When LOW, the counter counts up. The ripple clock output produces a low-level output pulse equal in width to the low-level portion of the clock input when an overflow or underflow condition exists.
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Synchronous operation is provided by hav- ing 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 count- ing spikes normally associated with asynchronous ripple clock counters. A HIGH at the enable input inhibits counting. The counter is 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 modulo-N divid- ers by simply modifying the count length with the preset inputs. The latter output produces a high-level output pulse with a duration approximately equal to one complete cycle of the clock when the counter overflows or underflows. The ripple clock output produces a low-level output pulse equal in width to the low-level portion of the clock input when an overflow or underflow condition exists.
The counters can be easily cascaded by feeding the ripple clock output to the enable input of the succeeding counter if parallel clocking is used, or to the clock input if parallel enabling is used.
74LS191 Contador Binario Sincrónico Arriba/Abajo
74LS191 - 74LS191 Up/Down Binary Counter