4013 D-type flip-flops


Posted on Feb 6, 2014

Next to the CLOCK input shows that it is edge-triggered, that is, it responds to sudden changes in voltage, but not to slow changes or to steady logic levels. The CLOCK input of the 4013 D-type bistable is rising-edge triggered, meaning that it responds only to a sudden change from LOW to HIGH. The inputs of the D-type must be connected, either to


4013 D-type flip-flops
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LOW or to HIGH, and must not be left open circuit. This includes the SET and RESET inputs which are connected to 0 V. To avoid loading the output of the D-type, a transistor switch indicator circuit is used. It is good practice with CMOS circuits to insert a decoupling capacitor, 47 µF or 100 µF, across the power supply. (This helps to prevent the transfer of spikes along the power supply rails. ) As you can see, the number of pulses at the output of the bistable is divided by two compared with the number of pulses at the input. A toggle bistable is a divide-by-two counter, or 1-bit binary counter. Can you see that the outputs give the binary numbers from 11 to 00 in descending order The circuit you have constructed is a 2-bit binary DOWN counter. D-type bistables can easily be used to make a combination lock. Using two 4013 integrated circuits, you can make a 4-digit combination lock in which the keys representing the code digits must be entered in the correct order. Pressing the key for any digit which is not part of the code RESETs all four D-types: goes HIGH. If the second digit is the next key presssed, the second D-type will be SET and so on. Pressing any of the unselected keys gives a HIGH at the RESET inputs of all four bistables, and all the Once the four digits of the code have been entered in the correct sequence, the lock ouptut goes HIGH and will remain HIGH until an unselected key is pressed. The system could...




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