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INTEGRATED CIRCUIT COUNTERS

الكلية كلية الهندسة     القسم  الهندسة الكهربائية     المرحلة 4
أستاذ المادة ايهاب عبد الرزاق حسين محمد       16/12/2016 18:54:22
INTEGRATED CIRCUIT COUNTERS
Integrated circuit counters are available for counter applications that require serial up or down count sequences. The IC counters available are 4-bit binary or decade counters that can be cascaded together for applications requiring more than four output stages. The IC counters have asynchronous inputs that allow the flexibility of presetting the counter to an initial start value other than zero or resetting the counter back to zero at any instant of time. The 74LS193 and 74LS90 are two IC counters that are used in examples throughout this chapter.
The 74LS193 Four-Bit Binary Counter
The 74LS193 is a 4-bit synchronous, positive edge-triggered, binary counter capable of counting up or down. It has two asynchronous inputs for presetting and clearing the counter.
The 74193 is a programmable counter to allow either up or down counting and complete control over the count modulus through the use of the asynchronous inputs. Two separate clock inputs are used to control up or down counting.
The counter has a maximum MOD-16 count sequence that can be shortened to any modulus less than 16 by using the asynchronous control inputs. The clear input resets all count stages back to zero. The preset input sets the counter stages to any 4-bit binary number loaded on the parallel inputs of the 74LS193.
The counter can be easily cascaded while counting up or down through the carry output and borrow output to lengthen the modulus and to provide additional counter output stages.
An example of using the asynchronous inputs on the 74LS193 is shown in Example (15).

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