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COMBINATIONAL LOGIC CIRCUITS

 COMBINATIONAL CIRCUITS

basically switching circuits maybe combinational switching circuit of sequential switching circuit. combinational switching circuits are those who to put level at any instant of time defence only on the levels presents at the inputs at the time. any Priya input level conditions have no effect on the present output, becomes combinational logic circuits have no memory. examples for logic gates, address, subtractor,multiplexers and demultiplexers circuits are widely used in the arithmetic logic unit section of microprocessor

 MULTIPLEXERS

multiplexes means many-to-one data selector logic circuit with many input but only one output it accepts several digital data input and only one of them give you one time epass drooping of the desired data input output is controlled by select functional data. the device has any input signal control signal 1 hour for example 16 to 1 multiplexer as 16 input signal four control select signal and 14 signal

APPLICATION

data selection
operation sequencing
waveform generation
data routing
parallel to serial conversion
logic function generation

figure 1.2 shows the logic symbol logic circuit and function table for a two input multiplexer the circuit consists of two and gates G1 and G2 and OR gate G3 and enogit G4 a and b are the data inputs and yes is the data select input the level applied to the US input enables one of the two and cakes and allows data input to pass through the OR gate to the output why Boolean expression for output why is

y =sa+SB

when is equal to zero get G4 output A1 to get jio one and a zero to get jeetu does jivan is enabled and jitu is disabled from output line mein goes to input line y and form b is blocked subtracting is equal to zero in equation I

y = 0 + b
10+0
A

this shows that output device follows input
when is equal to one get three four output a 0 to get g one and a to get G2 does jivan is disabled and G2 is enable data from input line goes to output line y and that from a is blocked substituting is equal to zero in the equation and even is disabled and G2 is enabled substitution s is equal to 1 in equation 1

USING 4 IS TO 1 MULTIPLEXER




considered the end gate shoes in the figure when both the inputs a and b are zero d0 is rooted with output y since the desired output is zero disconnected to the ground when a = 1 and b = 0 D2 is rooted to output why since the desired output is 1 2 3 is connected to the BCC similar explanation holds good for the realisation of other logic gates

multiplexer using 16 is 21 and forest 1 multiplexer

implementation of 64 in 1 multiplexer by using 416 is to 1 multiplexer and 1 to 1 multiplexer the four selected lines of all 16 is to 1 multiplexer are connected in parallel and are as 13 the output of 1681 are connected to the four output lines about the selected lines are the foods to 1 multiplexer and designed as 3 S4 and S5 input lines and designed and disconnected d0 263

assume that it is required to root data from to put the dress on the selected lines for this must be 3210 data from d 14 of all the 4 16 is to 1 multiplexer will flow through their respective to climb the inputs of the forest with S1 S2 data from d all the forest will be rooted with output why but corresponding to the 62 does data from BCC to close it out y

DEMULTIPLEXER

multiplexes takes several inputs and transmit one of them to the output perform the rivers operation means one to many logical with one input and output by applying control signals selectinput code we can root the input signal 21 of the clans in order the domestics takes one input data second and sensitivity towards the one and one output channels just like a multi portion switch the demultiplexer has one input signal control signal and output signal 1.68 the general idea
budh and gates the select line table only one date at the time the day today will pass through the enabled it look like when it is in 20 and it is enabled by the lower and get is disable data is transmitted only the why not given the value of y not depends on the value of the b doubt to doubt why one is in low state if the control put it change it to s = 1 the lower and gate is enabled while the upper and uric acid then is transmitted only provide 1 output and why I = expression for the output as follows

ENCODERS

encoding is a process of converting from family symbol on numbers recorded format it is performed biological called and translator

encoder has a number of input lines only one of which is activated at the given time it process and m bit output coded depends on which input is activated shows the general diagram of the witch and inputs and outputs

DECIMAL TO BCD ENCODER




decimal to BCD encoder converts each additional digits 0292 the binary coded accept input lines and produce a 4 bit output corresponding to the activated input is type of included as one of each digit and four output corresponding to the BCD code. BCD code from the table we can determine the relationship between each BCD bit and the decimal digits it can be seen that decimal digit input zero is not present in any of the expression none of the input is activated the input output will be low corresponding 2012 condition when any hi appears only one of the day decimal digit input lines 888 levels occurs on the four output line for instance if input line 535 resuming all other input divine are low this will produce output and see and do on this is BCD code 0101 for decimal 5

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