SN74F190A

The SN74F190A is a synchronous, 4-bit decade reversible up/down counter. Synchronous counting operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when so instructed by the steering logic. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple-clock) counters.

The SN74F190A outputs of the four flip-flops are triggered on a low-to-high-level transition of the clock (CLK) input if the enable (CTEN) input is low. A high at CTEN inhibits counting. The direction of the count is determined by the level of the down/up (D/U) input. When D/U is low, the counter counts up, and when D/U is high, it counts down. This SN74F190A counter features a fully independent clock circuit. Changes at the control (CTEN and D/U) inputs that modify the operating mode have no effect on the contents of the counter until clocking occurs. The function of the counter is dictated solely by the condition meeting the stable setup and hold times. This counter is fully programmable; that is, it may be preset to any number between 0 and 9 by placing a low on the load input and entering the desired data at the data inputs. The output changes to agree with the data inputs independent of the level of the clock input. This feature allows the counter to be used as a modulo-N divider by simply modifying the count length with the preset inputs.

SN74F190A Two outputs have been made available to perform the cascading function: ripple clock and maximum/minimum count. The latter output produces a high-level output pulse with a duration approximately equal to one complete cycle of the clock while the count is minimum (0) counting down or maximum (9) counting up. The ripple-clock (RCO) output produces a low-level output pulse under those same conditions, but only while the clock input is= low. The counter can easily be 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. The maximum/minimum count (MAX/MIN) output can be used to accomplish look-ahead for high speed operation.

The SN74F190A is characterized for operation from 0°C to 70°C.