Page 1 ENGIN112 L17: Encoders and Decoders October 10, 2003 Encoders and Decoders Page 2 ENGIN112 L17: Encoders and Decoders October 10, 2003 Encoders and Decoders ENGIN112 L17: Encoders and Decoders October 10, 2003 Overview ° Binary decoders Converts an n-bit code to a single active output Can be developed using AND/OR gates Can be used to implement logic circuits. ° Binary encoders Converts one of 2 n inputs to an n-bit output Useful for compressing data Can be developed using AND/OR gates ° Both encoders and decoders are extensively used in digital systems Page 3 ENGIN112 L17: Encoders and Decoders October 10, 2003 Encoders and Decoders ENGIN112 L17: Encoders and Decoders October 10, 2003 Overview ° Binary decoders Converts an n-bit code to a single active output Can be developed using AND/OR gates Can be used to implement logic circuits. ° Binary encoders Converts one of 2 n inputs to an n-bit output Useful for compressing data Can be developed using AND/OR gates ° Both encoders and decoders are extensively used in digital systems ENGIN112 L17: Encoders and Decoders October 10, 2003 Binary Decoder ° Black box with n input lines and 2 n output lines ° Only one output is a 1 for any given input Binary Decoder n inputs 2 n outputs Page 4 ENGIN112 L17: Encoders and Decoders October 10, 2003 Encoders and Decoders ENGIN112 L17: Encoders and Decoders October 10, 2003 Overview ° Binary decoders Converts an n-bit code to a single active output Can be developed using AND/OR gates Can be used to implement logic circuits. ° Binary encoders Converts one of 2 n inputs to an n-bit output Useful for compressing data Can be developed using AND/OR gates ° Both encoders and decoders are extensively used in digital systems ENGIN112 L17: Encoders and Decoders October 10, 2003 Binary Decoder ° Black box with n input lines and 2 n output lines ° Only one output is a 1 for any given input Binary Decoder n inputs 2 n outputs ENGIN112 L17: Encoders and Decoders October 10, 2003 2 2- -to to- -4 Binary Decoder 4 Binary Decoder ° From truth table, circuit for 2x4 decoder is: ° Note: Each output is a 2- variable minterm (X'Y', X'Y, XY' or XY) X YF 0 F 1 F 2 F 3 0 0 1 0 00 0 1 0 1 00 1 0 0 0 10 1 1 0 0 01 F 0 = X'Y' F 1 = X'Y F 2 = XY' F 3 = XY X Y Truth Table: 2-to-4 Decoder X Y F0 F1 F2 F3 Page 5 ENGIN112 L17: Encoders and Decoders October 10, 2003 Encoders and Decoders ENGIN112 L17: Encoders and Decoders October 10, 2003 Overview ° Binary decoders Converts an n-bit code to a single active output Can be developed using AND/OR gates Can be used to implement logic circuits. ° Binary encoders Converts one of 2 n inputs to an n-bit output Useful for compressing data Can be developed using AND/OR gates ° Both encoders and decoders are extensively used in digital systems ENGIN112 L17: Encoders and Decoders October 10, 2003 Binary Decoder ° Black box with n input lines and 2 n output lines ° Only one output is a 1 for any given input Binary Decoder n inputs 2 n outputs ENGIN112 L17: Encoders and Decoders October 10, 2003 2 2- -to to- -4 Binary Decoder 4 Binary Decoder ° From truth table, circuit for 2x4 decoder is: ° Note: Each output is a 2- variable minterm (X'Y', X'Y, XY' or XY) X YF 0 F 1 F 2 F 3 0 0 1 0 00 0 1 0 1 00 1 0 0 0 10 1 1 0 0 01 F 0 = X'Y' F 1 = X'Y F 2 = XY' F 3 = XY X Y Truth Table: 2-to-4 Decoder X Y F0 F1 F2 F3 ENGIN112 L17: Encoders and Decoders October 10, 2003 3 3- -to to- -8 Binary Decoder 8 Binary Decoder x y zF 0 F 1 F 2 F 3 F 4 F 5 F 6 F 7 0 0 0 1 0000000 0 0 1 0 1000000 0 1 0 0 0100000 0 1 1 0 0010000 1 0 0 0 0001000 1 0 1 0 0000100 1 1 0 0 0000010 1 1 1 0 0000001 F 1 = x'y'z x z y F 0 = x'y'z' F 2 = x'yz' F 3 = x'yz F 5 = xy'z F 4 = xy'z' F 6 = xyz' F 7 = xyz Truth Table: 3-to-8 Decoder X Y F0 F1 F2 F3 F4 F5 F6 F7 ZRead More

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