UNIVERSITI TEKNIKAL MALAYSIA MELAKA FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER DENC 2532 ECADD

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1 UNIVERSITI TEKNIKAL MALAYSIA MELAKA FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER DENC 2532 ECADD LAB SESSION 3 DIGITAL SIMULATION: MULTIPLEXER AND DEMULTIPLEXER Prepared by: Hamzah Asyrani Sulaiman Computer Engineering Department, FKEKK (September 2013)

2 LAB 3: DIGITAL SIMULATION - MULTIPLEXER AND DEMULTIPLEXER 1.0 OBJECTIVES After completing this lab session, you should be able: To demonstrate a basic Multiplexer and Demultiplexer system by using Multisim. To use Truth Table, Boolean algebra and Karnaugh Map to simplify the combinational logic circuit. To use logic analyzer tool in MultiSim to define the circuit output. 2.0 EQUIPMENT 2.1 Multisim Software 3.0 COMBINATIONAL LOGIC CIRCUIT DESIGN Multiplexer In electronics, a multiplexer or mux is a device that selects one of several analog or digital input signals and forwards the selected input into a single line. A multiplexer of 2n inputs has n select lines, which are used to select which input line to send to the output. An electronic multiplexer can be considered as a multiple-input, single-output switch i.e. digitally controlled multi-position switch. The digital code applied at the select inputs determines which data inputs will be switched to output. A multiplexer circuit works similar to a standard multi-way switch. It transmits the selected input directly to the single output. A common example of multiplexing or sharing occurs when several peripheral devices share a single transmission line or bus to communicate with computer. Each device in succession is allocated a brief time to send and receive data. At any given time, one and only one device is using the line. This is an example of time multiplexing since each device is given a specific time interval to use the line. Figure 1: Symbol of 4:1 MUX 2

3 Selection Input Output S1 S2 D 0 0 I I2 1 1 I3 Table 1: Truth Table of 4:1 MUX Demultiplexer A demultiplexer (or DEMUX) is a device taking a single input signal and selecting one of many data-output-lines, which is connected to the single input. A multiplexer is often used with a complementary demultiplexer on the receiving end. A demultiplexer is a single-input, multiple-output switch. Demultiplexers take one data input and a number of selection inputs, and they have several outputs. They forward the data input to one of the outputs depending on the values of the selection inputs. Demultiplexers are sometimes convenient for designing general purpose logic, because if the demultiplexer's input is always true, the demultiplexer acts as a decoder. This means that any function of the selection bits can be constructed by logically OR-ing the correct set of outputs. Demultiplexer is called as a distributor, since it transmits the same data to different destinations. Selection Input Output S1 S2 Y0 Y1 Y2 Y3 0 0 D D D D Table 2: Truth Table of 1:4 DEMUX Figure 2: Symbol of 1:4 DEMUX 3

4 4.0 TASK to-1 Line Multiplexer circuit simulation 1. Implement a 4:1 MUX on Multisim as shown in Figure 3. 1 XLA1 V1 U1 8kHz V2 U2 F 4kHz V3 U3 U5 C Q T OR4 2kHz V4 U4 1kHz VCC 5V S1 U6 NOT VCC 5V S0 U7 NOT Key = A Key = B Figure 3: 4-to-1 line Multiplexer circuit simulation 2. Run the simulation. Analyze the output and complete the truth table. Note: For demonstration purposes, the data inputs of the multiplexers are not all connected to static input values, but also to four clock generators with different clock periods. This should allow you to directly 'see' which input signal is transmitted by the multiplexer. 3. Implement a Boolean Function from the truth table. 4. Larger multiplexers can be constructed from smaller ones. A 16-to-1 multiplexer can be constructed from smaller multiplexers as shown below. Design the circuit in Figure 4 by using Multisim. 4

5 Figure 4: 16-to-1 multiplexer from 4:1 MUX 4.2 Multisim simulation of the Multiplexer Figure 4 shows the MultiSIM software simulation of the multiplexer. The object is to provide the capability to select one of the square wave signal sources (V0, V1 or V2) and route it to output terminal Y, which is monitored by the oscilloscope. The data selection lines A, B and C are used to select the desired input to be routed to Y. In this simulation the data selection lines are set to which chooses signal source V0. Notice that signal source V0 is a 1kHz waveform. The oscilloscope is displaying a waveform with a period of 1ms. This proves to be correct because 1/1kHz = 1ms. Also remember that the enable control input G', must be at the '0' level to enable the multiplexer to work. 5

6 1 XLA1 U3 V1 1kHz V2 2kHz V3 4kHz D0 D1 D2 D3 D4 D5 D6 D7 A B C ~G Y 5 ~W 6 F C Q T VCC 5V 74151N Key = A Key = B Key = C Key = G Figure 5: Multisim software simulation of the multiplexer 1. Double-click the oscilloscope to expand its size and then turn on the power simulation switch to perform the simulation shown in Figure Determine the state of the A-B-C selection switches to route the V1 waveform to the output. 3. Try it and make sure that the time period on the oscilloscope is correct for a 2kHz signal. 4. Repeat step (b) for V2. 5. While V2 is still being displayed, toggle the G' enable switch and describe what happens at Y. 6

Teaching Plan FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER UNIVERSITI TEKNIKAL MALAYSIA MELAKA

Teaching Plan FAKULTI KEJURUTERAAN ELEKTRONIK DAN KEJURUTERAAN KOMPUTER UNIVERSITI TEKNIKAL MALAYSIA MELAKA ECADD DENC 5 SEMESTER 1 SESI /014 DENC 5 ECADD 1.0 Learning Outcomes At the end of this subject,