encoder section 4.10. outline review: sum of products encoder priority decoder application of...
TRANSCRIPT
Encoder
Section 4.10
Outline
• Review: Sum of Products• Encoder• Priority Decoder• Application of Priority Decoder
Definition of an Encoder
• 2n 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 2n unique outputlines.
This particular circuit take a binary number and convert it to an octal number.
Review of ES112: Sum of Products
𝑓 1=𝑥 𝑦 𝑧+𝑥 𝑦 𝑧+𝑥𝑦𝑧
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 elementsoutput: Y, an array of 3 elementsV, a valid bit to check for 00000000 input.
Module Templatemodule module_name ( , , )
endmodule
Input, outputwiresreg
Program Body
Choosing a Module Namemodule module_name ( , , )
endmodule
Input, outputwiresreg
Program Body
Choosing a Module Namemodule module_name ( , , )
endmodule
Input, outputwiresreg
Program Body
x=D4+D5+D6+D7y=D2+D3+D6+D7z=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
Karnaugh Map
Circuit Implementation