Thursday, February 17, 2011

IC7490 DECADE COUNTER

Aim: To construct and verify the working of a single digit decade counter using IC 7490. Apparatus: 1) IC7490 Decade counter kit

2) Connecting patch cards.

Theory :- A decade counter is one that counts in decimal digits, rather than binary. A decade counter may have each digit binary encoded (that is, it may count in binary-coded decimal, as the 7490 integrated circuit did) or other binary encodings (such as the bi-quinary encoding of the 7490 integrated circuit).

Circuit Diagram :-                        OUTPUTS























Procedure:                                                    Fig:1

1.      Wire the circuit diagram shown in figure 1.

2.      Connect the 1Hz clock to pin CPO.(14)

3.      Connect the reset terminals (MR1 & MR2) to high and set terminals (MS1 & MS2) to zero and observe the output.

4.      Now connect set and reset inputs to zero and observe the outputs.

5.      Record the counter states for each clock pulse.

6.      Design mod 6 counter using IC 7490 as shown in fig 2.

7.      Record the counter states for each clock pulse.

8.      Now Construct decade counter using J – K F/F’s and record the counter states.


MOD 6 COUNTER      :




























Truth Table:-

A3 Msb
A2
A1
A0 Lsb








0
0
0
0








0
0
0
1








0
0
1
0








0
0
1
1








0
1
0
0








0
1
0
1
0000












0
1
1
0








Result:-   Verified the working of a single digit decade counter  using IC 7490.




4 – BIT BINARY RIPPLE COUNTER

Aim:      To  study the operation and working of a 4 – bit binary ripple counter using IC 7493

Apparatus:-

1.      4 – Bit binary ripple counter trainer kit.

2.      Set of Patch chords

Theory:
The ripple counter is simple and straightforward in operation and construction and usually
requires a minimum of hardware. It does, however, have a speed limitation. Each
flip-flop is triggered by the

previous flip-flop, and thus the counter has a cumulative settling time. Counters such as these are called serial or asynchronous.

The output Q0 must be externally connected to the input CP1. The input count pulses are applied to input CP0. Simultaneous divisions of 2, 4, 8 and 16 are performed at the Q0, Q1, Q2 and Q3 outputs as shown in the truth table.

A ripple counter can be constructed by use of clocked JK flip-flops. Fig shows four Master-Slaves, JK flip-flops connected in cascade. The system clock, a square wave, drives flip-flop A. the output of A drives B,

and output of B drives flip-flop C and output of C drives flip-flop D. All the J and K inputs are tied to +Vcc.

This means that each flip-flop will change state (toggle) with a negative transition at its clock input. When the output of a flip-flop is used as the clock input for the next flip-flop, we call the counter a ripple counter, or asynchronous counter. The A flip-flop must change states before it can trigger the B flip-flop, and the B flip-flop has to change states before it can trigger the C flip-flop. And the C flip-flop has to change states before it can trigger the D flip-flop the triggers move through the flip-flops like a ripple in water.
The waveforms given in fig show the action of the counter as the clock runs. Every time there is a negative clock transition, flip-flop A change state., Notice that the waveform at the output of flip-flop A is one half the clock frequency. Since A acts as a clock for B, each time the waveform at A goes low, flip-flop B will toggle. notice that the waveform at the output of flip-flop B is one half the frequency of A and one fourth the clock frequency. Since B acts as the clock for C, each time the waveform at B goes low, flip-flop C will toggle .The frequency of the waveform at C is one half that at B, but it is only one eight the clock frequency. Now C acts as a clock for D. Each time the wave form at C goes low,flip-flop D will toggle . The frequency of the waveform at D is one half that at C, but it is only one sixteenth the clock frequency.


Procedure:

1.       Switch ON the experimental board by connecting power chord to the AC mains.

2.      Connect the Bounceless pulser output to the clock input of 7493 counter.

3.      Verify the given  mode selection table.

Mod selection table

RESET INPUTS


OUTPUT






MR1
MR2
Q0
Q1
Q2
Q3






H
H
L
L
L
L
L
H


COUNT
H
L


COUNT
L
L


COUNT
Table  -   1

4.    Verify the truth table of the 7493 Ripple counter.
.

COUNT


OUTPUT







Q3
Q2

Q1
Q0






0
L
L

L
L






1
L
L

L
H






2
L
L

H
L






3
L
L

H
H






4
L
H

L
L






5
L
H

L
H






6
L
H

H
L






7
L
H

H
H






4-bit Ripple counter pin diagram :























Fig:1

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