Introduction

The 74LS193 is a 4-bit up/down binary counter with separate clock inputs for counting up and down. It is used in digital systems to count events or generate sequences and has two modes of operation: incrementing (up) and decrementing (down). In this experiment, we will demonstrate how to configure the 74LS193 IC to function as an up/down counter.

Materials Required

• 74LS193 Up/Down Counter IC
• Four LEDs (for displaying the 4-bit count)
• Resistors (220Ω for each LED)
• Breadboard and jumper wires
• Clock source (555 timer or manual clock button)
• Push buttons (for Up and Down clock inputs)
• Power supply (5V)

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Circuit Diagram

Below is the circuit diagram for the 74LS193 Up/Down Counter experiment:

Pin Configuration of the 74LS193

• Pin 1 (Q0): Least significant bit (LSB) output
• Pin 2 (Q1): Second bit output
• Pin 3 (Q2): Third bit output
• Pin 4 (Q3): Most significant bit (MSB) output
• Pin 5 (DOWN): Clock input for counting down
• Pin 6 (BO): Borrow output (active low during down counting)
• Pin 7 (GND): Ground
• Pin 8 (CLR): Clear input (active high)
• Pin 9 (LOAD): Load input (active low)
• Pin 10 (UP): Clock input for counting up
• Pin 11 (CO): Carry output (active low during up counting)
• Pin 12-15 (A-D): Parallel data inputs
• Pin 16 (VCC): Power supply

Steps for the Experiment

1. Place the 74LS193 IC on the breadboard.
2. Connect the Q0 to Q3 output pins to four individual LEDs with 220Ω resistors in series to ground. These LEDs will display the 4-bit binary count.
3. Connect two push buttons to the UP and DOWN clock input pins to provide manual clock pulses for counting up and down, respectively.
4. Connect the CLR (Clear) and LOAD pins to ground to disable their functions during normal counting.
5. Connect the power supply: 5V to the VCC pin and ground to the GND pin.
6. Press the UP button to increment the counter, and observe the LEDs lighting up in sequence according to the binary count.
7. Press the DOWN button to decrement the counter, and the LEDs will follow the reverse binary counting sequence.

Explanation

The 74LS193 has two clock inputs, one for counting up and one for counting down. When a pulse is applied to the UP clock input, the counter increments by one, and the output binary count is displayed on the LEDs. When a pulse is applied to the DOWN clock input, the counter decrements by one, and the LEDs reflect the reverse binary count. The 74LS193 is a synchronous counter, meaning all flip-flops are clocked simultaneously.

Results and Observations

As you press the UP button:

• The LEDs light up in sequence according to the binary count (0000 to 1111).
• Each press of the button increments the count by one, and the LED pattern changes accordingly.

As you press the DOWN button:

• The LEDs follow the reverse sequence, decrementing the count.
• The count decreases by one with each press, and the LED pattern reflects this change.

Applications of the 74LS193 Counter

The 74LS193 is commonly used in digital applications such as:

• Event counting (e.g., for time or frequency measurements)
• Sequence generation in state machines
• Frequency dividers
• Up/down counting in digital systems

Conclusion

In this experiment, we demonstrated the operation of the 74LS193 Up/Down Counter. The counter allows for both incrementing and decrementing, which is useful in digital systems for event counting, sequencing, and state transitions. By manually providing clock pulses, we observed how the counter increments and decrements in binary, with the output visible through the LEDs.