Given the inputs of a 8-to-3 priority encoder. Predict the output: Inputs Output

Question

Given the inputs of a 8-to-3 priority encoder. Predict the output:

Inputs                                                                                            Output

Y0       Y1       Y2       Y3       Y4       Y5       Y6       Y7                   A         B         C

0          1          0          0          1          0          0          0                     

1          1          1          0          0          0          0          0         

1          0          1          0          0          0          1          0

0          0          0          0          0          1          0          0

Explanation / Answer

Ans)

Priority Encoder:
A priority encoder provide n bits of binary coded output representing the position of the highest order active input of 2n inputs. If two or more inputs are high at the same time, the input having the highest priority will take precedence.
It's applications includes:
1.Used to control interrupt requests by acting on the highest priority request
2.To encode the output of a flash analog to digital converter

For an 8-to-3 binary encoder with inputs Y0-Y7 the logic expressions of the outputs A,B,C are:
A=Y1+Y3+Y5+Y7
B=Y2+Y3+Y6+Y7
C=Y4+Y5+Y6+Y7

For the first row output is:
       A=Y1+Y3+Y5+Y7
       Y1=1,Y3=0,Y5=0,Y7=0
A= 1 + 0 + 0 + 0= 1 (Take the highest priority 1)
     
   B=Y2+Y3+Y6+Y7
       Y2=0,Y3=0,Y6=0,Y7=0
       B=0 + 0 + 0 + 0= 0
   C=Y4+Y5+Y6+Y7
   Y4=1,Y5=0,Y6=0,Y7=0
   C=1 + 0 + 0 + 0=1
   So output for first row A,B,C is 1 0 1
  
For the second row output is:
       A=Y1+Y3+Y5+Y7
       Y1=1,Y3=0,Y5=0,Y7=0
A= 1 + 0 + 0 + 0= 1 (Take the highest priority 1)
     
   B=Y2+Y3+Y6+Y7
       Y2=1,Y3=0,Y6=0,Y7=0
       B=1 + 0 + 0 + 0= 1
   C=Y4+Y5+Y6+Y7
   Y4=0,Y5=0,Y6=0,Y7=0
   C=0 + 0 + 0 + 0=0
   So output for second row A,B,C is 1 1 0
  
For the third row output is:
       A=Y1+Y3+Y5+Y7
       Y1=0,Y3=0,Y5=0,Y7=0
A= 0 + 0 + 0 + 0= 0
     
   B=Y2+Y3+Y6+Y7
       Y2=1,Y3=0,Y6=1,Y7=0
       B=1 + 0 + 1 + 0= 1
      
   C=Y4+Y5+Y6+Y7
   Y4=0,Y5=0,Y6=1,Y7=0
   C=0 + 0 + 1 + 0=1
   So output for third row A,B,C is 0 1 1
  
For the fourth row output is:
       A=Y1+Y3+Y5+Y7
       Y1=0,Y3=0,Y5=1,Y7=0
A= 0 + 0 + 1 + 0= 1 (Take the highest priority 1)
     
   B=Y2+Y3+Y6+Y7
       Y2=0,Y3=0,Y6=0,Y7=0
       B=0 + 0 + 0 + 0= 0
      
   C=Y4+Y5+Y6+Y7
   Y4=0,Y5=1,Y6=0,Y7=0
   C=0 + 1 + 0 + 0=1
   So output for fourth row A,B,C is 1 0 1  
finally output is
               A B C
               1 0 1
               1   1 0
               0   1 1
               1       0 1

Related Questions

Navigate

• Browse (All)
• Browse G
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.