1. Lab 8 : Multiplexer and Demultiplexer Systems:
MUX :
Slide #2
DeMUX :
Slide #3
Security System Basics :
Slide #4
Security System Part 1 :
Slide #5
Security System Part 2 :
Slide #6
Using a MUX as a logic system :
Slide #7

2. Select inputs: 3 Bit number
Lab 8: The MUX :
An 8 channel multiplexer (MUX) is also called a 1 of 8 MUX. It’s function is to direct the flow of binary data from one input channel (I0 … I7) to the output Z. The channel is selected by a 3 bit code at S0, S1, S2. It is a data selector.
The input channels represent binary data from 8 different sources. Let’s assume the data is from 8 different computers (A … H).
The data from only one of these computers can be directed to Output Z.
The computer data is selected by the 3 bit number at inputs S2, S1, S0.
To select the data from Computer D you select I3 by setting S2=0, S1=1, S0=1 (binary 3). The other 7 computers are not selected.
The Z output allows the selected data to be inverted by the MUX.
MUX Z I2 I1 I3 I4 I5 I6 I7 I0 S0 S1 S2
Computer A
Computer B
Computer C
Computer D
Computer E
Computer F
Computer G
Computer H 1
Select inputs: 3 Bit number
Slide #2

3. Select inputs: 3 Bit number
Lab 8 : The DeMUX :
An 8 channel demultiplexer (DeMUX) is also called a 1 of 8 DeMUX. It’s function is to direct the flow of binary data from the single input channel (I) to one of the output channels (O0…O7). It is a data distributor.
The input channel represents binary data from one computer.
The data can be directed to only one of the outputs O0, … O7.
The output channel is selected by the 3 bit number input at S2, S1, S0.
To select O3 set S2=0, S1=1, S0=1 (binary 3). The other 7 output channels are not selected. They remain inactive at logic 0.
DEMUX I O2 O1 O3 O4 O5 O6 O7 O0 S0 S1 S2 1
Computer A
Select inputs: 3 Bit number
Slide #3

4. Lab 8 : Security System Basics :
Many security systems are used in buildings where the door’s to be monitored are at the back of the building and the monitor panel (LED’s) is at the front of the building. The distance between the panel and the doors can be large.
Let’s assume the security system has 8 doors. The doors are located at the back of the building.
A switch is mounted on each door indicates when it is opened. Door open =1 and closed =0.
An LED panel is used to signal which door is open.
The LED panel is located at front of building.
0 : Closed
0 : Closed
0 : Closed
1 : Opened
1 : Opened
1 : Opened 5V
Many wires must be connected, over long distances, from the doors to the LED’s.
A MUX/DeMUX security system will reduce the amount of wiring.
Slide #4

5. 7 6 4 5 2 Lab 8 : Security System Part 1:
A MUX/DeMux security system reduces the amount of wiring. It transfers the door data to the LED’s using 4 wires from the back of the building to the front.
Let’s begin with door 3 open and all other doors closed. The MUX will have Z=1 when the mod 8 counter is at binary 3 (011). The DeMUX selects output 3 and transfers data (inverse because the output is active low) to the LED. The LED lights as long as counter = 3.
The MUX will have Z=0 when the mod 8 counter is on any count other than binary 3 (011). The LED is off when the count is not = 3.
DEMUX I O2 O1 O3 O4 O5 O6 O7 O0 S0 S1 S2
MUX Z I2 I1 I3 I4 I5 I6 I7 I0 Q0 Q1 Q2
>Clk
Mod 8 Counter
Door 0
Door 1
Door 2
Door 3
Door 4
Door 5
Door 6
Door 7
10 PPS
Note: The Demux has active low outputs. The Demux will invert the door data. Thus Door = 1 will output a 0 from the demux and light the LED.
The counter has a 10 PPS clock. Each count state last 1/10th of a second each. Thus O3 activates the LED for 1/10th of a second for each 8/10th a second. This results in a blinking LED. 1 7 1 6 1 4 1 1 5 1 2 1 1
The 10 PPS clock is called the scan rate clock. Each door is connected to it’s corresponding LED for a 1/10th of a second. It takes 8/10th of a second to scan all doors. This is fast enough in order not to miss an intrusion. A high speed clock (1KPPS) would give the illusion that the LED is continuously on. The blink rate of 1 milliSec is too fast to detect the LED turning off.
Slide #5

6. 2 2 2 3 3 4 6 7 7 5 4 4 3 5 6 6 7 5 Lab 8 : Security System Part 2:
The operation of the system will be demonstrated with two doors opened at the same time. Door 1 and Door 5 are both opened the other doors are closed.
The system operates quickly and it is difficult to observe all the changes at one time. Concentrate on the counter section. You will see it cycle from 0 to 7.
Concentrate on the MUX section. Each door is scanned as the counter cycles from 0 to 7.
Concentrate on the DeMUX section. LED’s at O1 and O5 light up sequentially as counter cycles from 0 to 7.
DEMUX I O2 O1 O3 O4 O5 O6 O7 O0 S0 S1 S2
MUX Z I2 I1 I3 I4 I5 I6 I7 I0 Q0 Q1 Q2
>Clk
Mod 8 Counter
Door 0
Door 1
Door 2
Door 3
Door 4
Door 5
Door 6
Door 7
10 PPS
Note: The Demux has active low outputs. The Demux will invert the door data. Thus Door = 1 will output a 0 from the demux and light the LED. 1 1 1 1 1 2 1 2 1 2 1 3 1 3 1 4 1 6 1 7 1 7 1 5 1 4 1 4 1 3 1 5 1 6 1 6 1 7 1 5
Slide #6

7. 2 3 1 4 Lab 8 : Using a MUX as a logic gate system :
A mux can be used to construct an entire logic gate system. This was once an important fact that allowed older IC technology designers to replace many single function logic gate TTL IC’s with a single mux IC. System changes are also easily accommodated.
The system we are trying to build has Boolean equation Z = ABC + ABC + ABC + ABC
A standard logic gate system using older generation TTL technology would require 4 IC’s.
The first step used to design a MUX logic gate system is to generate the truth table. 1 2 3 4
The second step is to connect the MUX inputs directly to 5V or ground as indicated by the truth table.
The third step is to connect the MUX select to the inputs of the logic gate system. Connect MSB to S2.
The output of the system is taken from Z.
The result is a 1 IC system that can be easily changed. A system change can be accommodated by a change of 5V or ground connection at the input of the MUX.
Connect I0 to 5V because Z=1 in the truth table A B C Z 1 5V
MUX Z I2 I1 I3 I4 I5 I6 I7 I0 S0 S1 S2
ABC
Connect I1 to GND because Z=0 in the truth table
Continue …
Output C
Slide #7 B A