{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

04 Combinational Logic Circuit Design

# 04 Combinational Logic Circuit Design - EE2000 Logic...

This preview shows pages 1–13. Sign up to view the full content.

1 EE2000 Logic Circuit Design 4 Combinational Logic Circuit Design ±±±

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 Outline ± 4.1 Design Procedure ± 4.2 Design Examples ± Staircase Lighting Circuit ± Code Converter Circuit ± Seven-Segment Display Circuit ± 4.3 Design Issues ± Timing Hazard
3 4.1 Design Procedure ± 1) Specification ± Write a specification for the circuit ± 2) Formulation ± Derive the truth table (or initial Boolean equations) to define the relationships between inputs and outputs ± 3) Optimization ± Apply logic circuit optimization ± 4) Technology Mapping ± Transform logic diagram to a new diagram using available implementation technology ± 5) Verification ± Verify the correctness of the final design

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
4 4.2 Design Examples
5 4.2.1 Staircase Lighting Circuit On/Off Button A On/Off Button B On/Off Button A On/Off Button B = On/Off Button A On/Off Button B = On/Off Button A On/Off Button B = On/Off Button A On/Off Button B =

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
6 4.2.1 Staircase Lighting Circuit ± Specification: ± Design of a staircase lighting circuit ± There are two input buttons namely A & B ± The bulb will light on if both buttons have been turned up or down. It will light off if one button is up and the other one is down On/Off Button A On/Off Button B ? A B F
7 Formulation ± Derive the truth table relating input and output variables from specification ± Optimization: ± From the truth table, ± F ( A , B ) = AB + A’B’ (= A B) Inputs Output A B F 0 0 1 0 1 0 1 0 0 1 1 1 F ( A , B ) is 1 if (A = 0 AND B = 0) OR (A = 1 AND B = 1) i.e. F ( A , B ) = A’B’ + AB = Σ m (0, 3)

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
8 The Final Logic Diagram A B F = A’B’ + AB On/Off Button A On/Off Button B ? A B F A B F = A B
9 4.2.2 Code Converter Circuit ± Specification: ± Design of a BCD-to-Excess-3 Code Converter ± XS3 code for a decimal digit is the binary combination corresponding to the decimal digit plus 3 ± Each BCD digit labeled from MSB, A , B , C , D ± The XS3 digit labeled from MSB, W , X , Y , Z ± i.e. ( ABCD ) BCD = ( WXYZ ) XS3

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
10 The Rough Picture ± Design a logic circuit that perform code conversion ± Input is BCD 8421 code ± Output is Excess-3 code A B C W X Y Z D Excess-3 code BCD code ? (MSB) (LSB) (MSB) (LSB)
11 Formulation Decimal digit Input (BCD 8421 Code) Output (Excess-3 Code) A B C D W X Y Z 0 0 0 0 0 0 0 1 1 1 0 0 0 1 0 1 0 0 2 0 0 1 0 0 1 0 1 3 0 0 1 1 0 1 1 0 4 0 1 0 0 0 1 1 1 5 0 1 0 1 1 0 0 0 6 0 1 1 0 1 0 0 1 7 0 1 1 1 1 0 1 0 8 1 0 0 0 1 0 1 1 9 1 0 0 1 1 1 0 0 Unused 1 0 1 0 x x x x Unused 1 0 1 1 x x x x unused 1 1 0 0 x x x x Unused 1 1 0 1 x x x x Unused 1 1 1 0 x x x x Unused 1 1 1 1 x x x x Some input combinations are illegal as they are no meaning in BCD code. We can treat the corresponding outputs as don’t care

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Optimization ± There are four variables ( A , B , C , D ) in the functions ± Each output variable depends on 4 variables ± So we need 4 four-variable K-maps ± W ( A , B , C , D ) = Σ m (5, 6, 7, 8, 9) + Σ d (10, 11, 12, 13, 14, 15) ± X ( A , B , C , D ) = Σ m (1, 2, 3, 4, 9) + Σ d (10, 11, 12, 13, 14, 15) ± Y ( A , B , C , D ) = Σ m (0, 3, 4, 7, 8) +
This is the end of the preview. Sign up to access the rest of the document.
• Spring '07
• VanCWTing
• Logic gate, timing diagram, Combinational Logic Circuits, Staircase Lighting Circuit, timing hazards, 7-segment display circuit

{[ snackBarMessage ]}

### Page1 / 47

04 Combinational Logic Circuit Design - EE2000 Logic...

This preview shows document pages 1 - 13. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online