It has n input and to a maximum m 2n outputs Decoder is identical to a

# It has n input and to a maximum m 2n outputs decoder

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A decoder is a combinational circuit. It has n input and to a maximum m = 2n outputs. Decoder is identical to a demultiplexer without any data input. It performs operations which are exactly opposite to those of an encoder. Examples of Decoders are following. Code converters BCD to seven segment decoders Nixie tube decoders Relay actuator Comp Architecture - Digital Computer 44
Diagram and truth table Comp Architecture - Digital Computer 45
Encoder Perform the inverse operation of the decoder. An encoder has n number of input lines and m number of output lines. The encoder accepts an n input digital word and converts it into an m bit another digital word. Examples of Encoders are following. Priority encoders Decimal to BCD encoder Octal to binary encoder Hexadecimal to binary encoder Comp Architecture - Digital Computer 46
SEQUENTIAL CIRCUITS Comp Architecture - Digital Computer 47
Sequential Circuits The combinational circuit does not use any memory. Hence the previous state of input does not have any effect on the present state of the circuit. But sequential circuit has memory so output can vary based on input. This type of circuits uses previous input, output, clock and a memory element. Comp Architecture - Digital Computer 48
Comp Architecture - Digital Computer 49
Flip Flop Flip flop is a sequential circuit which generally samples its inputs and changes its outputs only at particular instants of time and not continuously. Flip flop is said to be edge sensitive or edge triggered rather than being level triggered like latches Comp Architecture - Digital Computer 50
S-R Flip Flop It is basically S-R latch using NAND gates with an additional enable input. It is also called as level triggered SR-FF. For this circuit in output will take place if and only if the enable input (E) is made active. In short this circuit will operate as an S-R latch if E= 1 but there is no change in the output if E = 0 Comp Architecture - Digital Computer 51
Comp Architecture - Digital Computer 52
Truth Table Comp Architecture - Digital Computer 53

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• Fall '19
• Boolean Algebra, Logic gate, Combinational Circuits,  Examples of the digital systems

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