Encoder

This presentation is about Encoder; a topic digital logic circuits and design

1. GREEN UNIVERSITY OF BANGLADESH ENCODER

2. What is Encoder? Combinational circuit Performs the reverse operation of Decoder Maximum of input lines and output lines   ENCODER INPUTS   OUTPUTS  

3. Generates an output based on the highest prioritized input Binary Priority Types of Encoder Converts one of inputs into an bit output  

4. 4 – 2 Encoder 4 inputs: , ,   2 outputs: ,   4 - 2 ENCODER             Block diagram

5. 4 – 2 Encoder 4 inputs: , ,   2 outputs: ,   4 - 2 ENCODER 1 1 Block diagram

6. INPUTS OUTPUTS 1 1 1 1 1 1 1 1 INPUTS OUTPUTS 1 1 1 1 1 1 1 1 4 – 2 Encoder Truth Table

7. INPUTS OUTPUTS 1 1 1 1 1 1 1 1 INPUTS OUTPUTS 1 1 1 1 1 1 1 1 4 – 2 Encoder Truth Table  

8. INPUTS OUTPUTS 1 1 1 1 1 1 1 1 INPUTS OUTPUTS 1 1 1 1 1 1 1 1 4 – 2 Encoder Truth Table  

9. Boolean functions   Circuit diagram

10. 8 – 3 Encoder 8 inputs: , , , , , ,   3 outputs: , ,               Block diagram         4 - 2 ENCODER   8 - 3 ENCODER

11. 8 – 3 Encoder 8 inputs: , , , , , ,   3 outputs: , ,             Block diagram         4 - 2 ENCODER   8 - 3 ENCODER

12. 8 – 3 Encoder Truth Table INPUTS OUTPUTS 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 INPUTS OUTPUTS 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

13. Boolean functions   Circuit diagram

14. Drawbacks of Encoder W hen all outputs of encoder are equal to zero . If more than one input is active High, then the encoder produces an output, which may not be the correct code.

15. Priority Encoder .

16. 4 – 2 Priority Encoder Truth Table INPUTS OUTPUTS Y3 Y2 Y1 Y0 A1 A0 V 1 1 1 X 1 1 1 X X 1 1 1 X X X 1 1 1 X equals “ dont care”, that is it can be at a logic “0” level or at a logic “1” level

17. 4 – 3 Priority Encoder INPUTS OUTPUTS Y3 Y2 Y1 Y0 A1 A0 V 1 1 1 X 1 1 1 X X 1 1 1 X X X 1 1 1 Lowest priority Highest priority To check the output is valid or not

18. 4 variable K-maps Boolean functions A1 = Y3 + Y2 A0 = Y3 + Y2’Y1 Boolean function of output, V  V = Y3 + Y2 + Y1 + Y0

19. THANK YOU.

20. Reference: https://www.tutorialspoint.com/digital_circuits/digital_circuits_encoders.htm https://www.geeksforgeeks.org/encoder-in-digital-logic/ https://www.electronics-tutorials.ws/combination/comb_4.html https://www.electronics-tutorials.ws/combination/comb_4.html Digital design by Morris M ano and Michael D.Ciletti