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ECE 301 – Digital Electronics

Circuit Design and Analysis (Lecture #9A). ECE 301 – Digital Electronics. The slides included herein were taken from the materials accompanying Fundamentals of Logic Design, 6 th Edition , by Roth and Kinney, and were used with permission from Cengage Learning. Logic Circuits.

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ECE 301 – Digital Electronics

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  1. Circuit Design and Analysis (Lecture #9A) ECE 301 – Digital Electronics The slides included herein were taken from the materials accompanying Fundamentals of Logic Design, 6th Edition, by Roth and Kinney, and were used with permission from Cengage Learning.

  2. ECE 301 - Digital Electronics Logic Circuits • Combinational Logic Circuits • Output is a function of the inputs. • Output is not a function of the order of the inputs. • No memory is required. • Sequential Logic Circuits • Output is a function of the state of the circuit and the inputs. • Output is a function of the history of the inputs. • Requires memory.

  3. ECE 301 - Digital Electronics Circuit Design

  4. ECE 301 - Digital Electronics Circuit Design • For a given logic function, two two-level logic circuits can be realized. • An AND-OR (NAND-NAND) circuit • An OR-AND (NOR-NOR) circuit • However, these two logic circuits do not necessarily have the same cost. • An objective of the digital circuit designer is to minimize the cost of the circuit to be built.

  5. ECE 301 - Digital Electronics Circuit Design Issues • More than one circuit may meet the design requirements. • Solutions are, generally, not unique • Cannot always satisfy all of the requirements. • Design tradeoffs must be identified and considered. • Cost • Speed • Power consumption

  6. ECE 301 - Digital Electronics Design Procedure • Identify the requirements (i.e. circuit specifications) • Determine the inputs and outputs • Derive the truth table • Determine the minterm and maxterm expansions • Use K-maps (and Boolean algebra), to derive the minimum SOP and POS expressions • Compare the costs of the two expressions • Build (or synthesize) the “cheaper” circuit • Verify the functional behavior of the circuit

  7. ECE 301 - Digital Electronics Design a combinational logic circuit that meets the following requirements: 1. Outputs a logic 1 for all values in the Fibonacci series between 0 and 7. 2. Outputs a logic 0 otherwise. Circuit Design: Example #1

  8. ECE 301 - Digital Electronics Questions: 1. What is the Fibonacci Series? 2. How many bits are needed to represent the input? 3. How many bits are needed to represent the output? Circuit Design: Example #1

  9. ECE 301 - Digital Electronics Design in progress … Circuit Design: Example #1

  10. ECE 301 - Digital Electronics Design a 7-Segment Decoder. Circuit Design: Example #2

  11. ECE 301 - Digital Electronics Circuit Design: Example #2 7 outputs 4 inputs BCD Number 7-Segment Decoder 7-Segment Display

  12. ECE 301 - Digital Electronics Binary Coded Decimal • A 4-bit code is used to represent each decimal digit.

  13. ECE 301 - Digital Electronics 7-Segment Display

  14. ECE 301 - Digital Electronics 7-Segment Display

  15. ECE 301 - Digital Electronics Design in progress … Circuit Design: Example #2

  16. ECE 301 - Digital Electronics Circuit Analysis

  17. ECE 301 - Digital Electronics Circuit Analysis • Analyze a logic circuit to determine its behavior. • For a two-level circuit, the analysis process is simple. • Boolean expression can often be written by inspection. • For multi-level circuits, the process is more complex. • Cannot write a Boolean expression by inspection. • Must follow a procedure to implement the analysis.

  18. ECE 301 - Digital Electronics Analysis Procedure • Identify the circuit inputs and output(s). • Track the logical behavior from input to output. • Determine the Boolean expression for the output(s). • Derive the truth table for the output(s). • Evaluate the electrical and timing characteristics of the circuit.

  19. ECE 301 - Digital Electronics Analyze the following logic circuit: 1. Determine the Boolean expression 2. Derive the truth table A B' C F D' E Circuit Analysis: Example

  20. ECE 301 - Digital Electronics Questions?

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