Experiment-10 Asynchronous Counter

AIM

Design, and verify the 4-bit asynchronous counter.

OBJECTIVE:

i).To understand the design of a sequential circuits.

ii)To implement the theory with a real circuit and verify the working.

THEORY:

Asynchronous counters, also known as ripple counters, are not clocked by a common pulse and hence every flip-flop in the counter changes at different times. The flip-flops in an asynchronous counter is usually clocked by the output pulse of the preceding flip-flop. The first flip-flop is clocked by an external event. A synchronous counter however, has an internal clock, and the external event is used to produce a pulse which is synchronised with this internal clock. The diagram of a ripple counter is shown below Logic Circuit:

Operation and waveform:

Since the J and K input are tied to high voltage, each flip-flop will toggle when its clock receives positive input. When CLR input goes low, all flip-flop are reset and the output Q3Q2Q1Q0=0000.

When the CLR returns to high, the counter is ready to go. Since least significant (1st ) flip-flop receives the clock pulse, Q0 toggles once per positive clock pulse. The rest of the flip-flop toggles less often because they receive their positive edge pulse from the Q output of the preceding flip-flop.

When Q0 changes from 0 to 1, Q1 flip-flop receives +ve edge and toggles. Likewise, when Q1 changes from 0 to 1, Q2 gets a +ve edge and will toggle. And finally when Q2 changes from 0 to 1, Q3 flip-flop toggle. In otherwords, whenever a FF sets to 1, the next higher FF toggle. To see how it goes, see the waveform.

Precaution:

  • All ICs should be checked before starting the experiment. Keep PIN Diagram of IC with you
  • All the connection should be tight.
  • Always connect ground first and then connect Vcc.
  • Suitable type wire should be used for different types of circuit.
  • Power-off before changing the connections.
  • After completed the experiments switch off the supply of the apparatus

Preparation:

i).Refer the PIN diagram of all required IC for connections.

ii.Switch off the Power Supply

  1. Fix up the ICs on the breadboard and connect properly
  2. Check the connections for correctness
  3. Connect the power

Requirement:

IC 747602LED04

220 Ohm Resistor04Function Generator

Implementation:

Verification:

Apply the input/ clock ( 1-10 Hz) and observe the pattern on LED and verify with the theory.