SCAS105A - FEBRUARY 1990 - REVISED APRIL 1993
m Process
EPIC is a trademark of Texas Instrumentsdescription
The 74AC11191 is a synchronous, 4-bit binary reversible up/downcounter. Synchronous counting operation is provided by clocking allflip-flops simultaneously so that the outputs change coincident witheach other when instructed by the steering logic. This mode ofoperation eliminates the output counting spikes normally associatedwith asynchronous (ripple clock) counters.
The outputs of the four flip-flops are triggered on alow-to-high-level transition of the clock input if the enable input(
) is low. Ahigh at inhibitscounting. The direction of the count is determined by the level ofthe down/up (D/U\) input. When D/U\ is low, the counter counts up andwhen D/U\ is high, it counts down.
These counters feature a fully independent clock circuit. Changesat the control inputs ( andD/U\) that will modify the operating mode have no effect on thecontents of the counter until clocking occurs. The function of thecounter will be dictated solely by the condition meeting the stablesetup and hold times.
These counters are fully programmable; that is, the outputs may bepreset to any number between 0 and 15 by placing a low on the loadinput and entering the desired data at the data inputs. The outputswill change to agree with the data inputs independently of the levelof the clock input. This feature allows the counter to be used as amodulo-N divider by simply modifying the count length with the presetinputs.
Two outputs have been made available to perform the cascadingfunction: ripple clock and maximum/minimum count. The latter outputproduces a high-level output pulse with a duration approximatelyequal to one complete cycle of the clock while the count is zero (alloutputs low) counting down or maximum (15) counting up. Theripple-clock output (
)produces a low-level output pulse under those same conditions butonly while the clock input is low. The counter can easily be cascadedby feeding the ripple clock output to the enable input of thesucceeding counter if parallel clocking is used, or to the clockinput if parallel enabling is used. The maximum/minimum count outputcan be used to accomplish look-ahead for high-speed operation.
The 74AC11191 is characterized for operation from - 40°C to85°C.
View more information about generic part numbers:74AC11191
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