## 8 letter message, ‘BLuEFiSh’, to 7-segment display conversion

A 7-segment display is used to show a message letter associated with each count of 0 to 7 and is

driven from a 3-bit input (A,B,C). So that 0->’B’, 1->’L’, 2 ->’u’, 3-> ‘E’, 4->’F’, 5->’i’, 6->’S’, 7->’h’.

Each segment is assumed to light up when a logical 1 is applied to it.

1. Draw the truth table to drive segments (a-g) of the display.

2. Using the truth table you have obtained, draw Karnaugh maps for each segment to find the

minimised logic expression in the 1-st canonical form (SOP, i.e. series of AND terms ORed

together).

3. Convert the expression from 2 to a function which uses only NAND gates and draw the

equivalent circuit diagram in Logic Circuit and generate its truth table to compare with 1.

4. Draw the Karnaugh map which corresponds to the 2-nd canonical form of the truth table you

found in 1. Use this to find the minimised logic expression in the 2-nd canonical form (POS,

i.e. a series of OR terms ANDed together).

5. Write the expression from 4 as a function which uses only NOR gates and draw the equivalent

circuit diagram in Logic Circuit and generate its truth table to compare with 1.

6. Compare diagrams from 3 and 5. Which of them is more simple?

7. Show that the circuit from 3 and 5 can draw the message digits correctly by using Logic Circuit

to create a simulation file to show a 7 – segment display from a set of three switches

representing inputs A, B, C.

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