Encoder Section 4.10

Outline Review: Sum of Products Encoder Priority Decoder Application of Priority Decoder

Definition of an Encoder 2 n input lines n output lines Performs the inverse operation of a decoder

Review: 3-to-8 Line Decoder Convert binary information from n input lines to 2 n unique output lines. This particular circuit take a binary number and convert it to an octal number.

Review of ES112: Sum of Products

Hardware Implementation

Example of 8-to-3 Encoder

Application of 8 x 3 Encoder The angular or rotary position of a compass is converted into a digital code by an encoder and inputted to the systems computer to provide navigational data

Implementation of an Encoder Focus on one output at a time x=D4+D5+D6+D7

Implementation of an Encoder Focus on one output at a time y=D2+D3+D6+D7

Implementation of an Encoder Focus on one output at a time z=D1+D3+D5+D7

Uncertainty of an Encoder What if all the input lines are 0? – Use a valid bit

Model an Encoder in Verilog input : D, an array of 8 elements output: Y, an array of 3 elements V, a valid bit to check for input.

Module Template module module_name (,, ) endmodule Input, output wires reg Program Body

Choosing a Module Name module module_name (,, ) endmodule Input, output wires reg Program Body

Choosing a Module Name module module_name (,, ) endmodule Input, output wires reg Program Body x=D4+D5+D6+D7 y=D2+D3+D6+D7 z=D1+D3+D5+D7 Or all elements of D

Output File D={D0,D1,D2,D3,D4,D5, D6,D7} Y={Y0,Y1,Y2} (least significant to most significant}

Output File The output with a higher subscript has a higher priority than an output with a lower subscript.

Priority Encoding What if more than one input line are high? – Use priority—certain bits are more important than other bits

Priority Encoder Not a Valid State

Karnaugh Map 1

Circuit Implementation