Introduction
A simple 2 to 1 multiplexer is demonstrated in this experiment. One of the data input of multiplexer is connected to VCC & the other is connected to GND. Connecting to GND & VCC shows two different signal level for two different channels. The channel selection logic is controlled by the user via the manual stimulus circuit.
Components:
1. One CD4081 IC (AND Gate)
2. One CD4069 IC (NOT Gate)
3. One CD4071 IC (OR Gate)
4. One 2.2KΩ Resistor, One 10KΩ Resistor
5. One tap switch
6. One LED (any color)
(The experiment can be conducted more efficiently with Terminus. To show output from different sources, this experiment can use Terminus. The Oscillator and the power VCC is used to generates two different types of signals to simulate data transmission.)
Steps:
1. Construct the circuit as shown in the schematic
2. Construct the manual stimulus generator using resistor and switch used/shown earlier
3. Power ON the circuit
3. Push the channel selection tap switch and observe the outputs and its corresponding inputs and note them down
4. Release the tap switch and observe the outputs and its corresponding inputs and note them down
5. At the end of the experiment, compare the noted values with the truth table and the theory
Explanation:
From the circuit, one input of both AND gate is connected to an individual data input i.e. S0 and S1. The remaining input of the AND gates are connected to the Date_select input. One of them is connected directly, and the other via a NOT gate. The input of the NOT gate is the Data_selection input.
AND gate requires both inputs to be HIGH to show a HIGH on the output. If one of the input is connected to a LOW, the entire output becomes LOW regardless of the state of the other input. This way, an AND gate can be used like a digital switch that can control the flow of data. One of the input is connected to the data source and another input is connected to the switching Logic. If we need data to pass through the AND gate, we make the switching logic pin HIGH. If the state on the other pin is 1, the output is 1 (1 AND 1 = 1). If the state of the other pin is 0, the output is 0 (0 AND 1 = 0). To disable data flow, we make the switching logic pin 0 and force the output of the AND gate to 0. No matter the state of the data pin the output of the AND gate stays 0. This principle is used in making the multiplexer.
The multiplexer has two AND gates and one NOT gate. One AND gate input is connected directly to the Data_selector. Another AND gate input is connected to the Data_selector via a NOT gate. This way when one AND gate is enabled, the other one is disabled. This setup allows the data from only one AND gate to pass through. The data is later combined to pass through a single wire by using an OR gate.
The data inputs of the multiplexer is connected to two different types of signal. The VCC will provide with a steady Logic HIGH. The GND will provide with a steady Logic LOW. This two different types of inputs allows us to show that different input signals are connected to the output by changing the input on the Selection pin. When the Data_select pin is LOW, S0 input is connected to the output. S0 is connected to VCC i.e. the input is at steady HIGH. Therefore, the output of the multiplexer will also be HIGH. When the Date_select is at HIGH, S1 is connected to the output. S1 is connected to the GND. Therefore, the output will also show a logic LOW.
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