OutlineOutline
Analysis of Sequential CircuitsRipple counters
fDesign of Divide-by-N CountersRipple Counter ICs
lSystem Design Applications7-Segment LED Display DecodersS h C tSynchronous CountersSynchronous Up/Down-Counters ICsA li ti f S h C t IC
Ch. 12: Counter Circuits 2
Applications of Synchronous Counters ICs
12 2 Ripple counters12.2 Ripple countersA counter circuit can be built by cascading flip-flops together. (Connecting the Q output of one flip flop to the clock input of the(Connecting the Q output of one flip-flop to the clock input of the next) The number of states in a counter (modulus) is 2N where N is the number of flip-flops.number of flip flops. In order for a counter to operate properly each flip-flop must toggle. For J-K flip-flops this means both J and K must be high. In a ripple counter the clock input has to propagate through each pp p p p g gflip-flop of the counter. A ripple counter is also called an asynchronous counter because each flip-flop does not change at the same time. The propagation delay of each flip-flop adds together to give a total propagation delay for the counter. This propagation delay will limit the maximum frequency allowed by the input trigger clock. A down counter can be formed by taking the output from the
Ch. 12: Counter Circuits 4
A down counter can be formed by taking the output from the output instead of the Q output of each flip-flop.
12.3 Design of Divide-by-N g yCounters
A counter can also be used as a frequency divider. q y
Ch. 12: Counter Circuits 8
12 4 Ripple Counter ICs12.4 Ripple Counter ICs
7490 (mod 2 x 5)7492 (mod 2 x 6)7492 (mod 2 x 6)7493 (mod 2 x 8)
Ch. 12: Counter Circuits 12
12 5 System Design Applications12.5 System Design Applications
Digital ClockTimer UpTimer UpTimer Down
Ch. 12: Counter Circuits 17
KuisKuis
Count up 34563456, 4567845678Count down 65436543: 8765487654Count down 65436543: 8765487654Timer up 012345 : 012345678Ti d 543210 876543210Timer down 543210: 876543210
Ch. 12: Counter Circuits 24