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Logic Networks/Seven Segment Displays

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Fr33t
#1
Sep23-10, 12:34 AM
P: 2
1. The problem statement, all variables and given/known data
Here's the problem:

Design a logic network that can display the characters in “APPLE” on a sevensegment
display unit. Write the truth table for the output functions C0-C6, minimize them
by using Karnaugh Map, and implement using discrete logic gates.
(Hints: Character “A” will be displayed if segments (C0, C1, C2, C4, C5, C6) of a 7-
segment display are turned on and segment (C3) is turned off. Since only 4 characters
will be displayed, input of 2 bits to encode them will be needed for the given design.)

Now, where I get confused is when it says an input of 2 bits to encode them will be needed. I understand that technically only 2 bits are needed, but I do not understand how to implement it using only 2 instead of 4. I've been searching and thinking of different ways to do it but I am stumped.

2. Relevant equations
Not quite applicable


3. The attempt at a solution
With 2 bits to work with:
00 = A
01 = P
10 = L
11 = E
A	B	C0	C1	C2	C3	C4	C5	C6
0	0	1	1	1	0	1	1	1
0	1	1	1	0	0	1	1	1
1	0	0	0	0	1	1	1	0
1	1	1	0	0	1	1	1	1
But what is the point of using a K Map for this? I am almost sure this is where I am wrong but I have no idea what to do?

Any help will be greatly appreciated! Thanks
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berkeman
#2
Sep23-10, 12:39 PM
Mentor
berkeman's Avatar
P: 40,634
Quote Quote by Fr33t View Post
1. The problem statement, all variables and given/known data
Here's the problem:

Design a logic network that can display the characters in “APPLE” on a sevensegment
display unit. Write the truth table for the output functions C0-C6, minimize them
by using Karnaugh Map, and implement using discrete logic gates.
(Hints: Character “A” will be displayed if segments (C0, C1, C2, C4, C5, C6) of a 7-
segment display are turned on and segment (C3) is turned off. Since only 4 characters
will be displayed, input of 2 bits to encode them will be needed for the given design.)

Now, where I get confused is when it says an input of 2 bits to encode them will be needed. I understand that technically only 2 bits are needed, but I do not understand how to implement it using only 2 instead of 4. I've been searching and thinking of different ways to do it but I am stumped.

2. Relevant equations
Not quite applicable


3. The attempt at a solution
With 2 bits to work with:
00 = A
01 = P
10 = L
11 = E
A	B	C0	C1	C2	C3	C4	C5	C6
0	0	1	1	1	0	1	1	1
0	1	1	1	0	0	1	1	1
1	0	0	0	0	1	1	1	0
1	1	1	0	0	1	1	1	1
But what is the point of using a K Map for this? I am almost sure this is where I am wrong but I have no idea what to do?

Any help will be greatly appreciated! Thanks
Welcome to the PF.

Everything you've done looks correct. Now just do the 7 K-maps (or just write the 7 equations) that define the logic that drives the 7-segment displays. The same logic is repeated at each display, and drives the 7 segments based on that 2-bit input AB.

BTW, I edited your post to insert Code tags around your table. This preserves the column alignment.
Fr33t
#3
Sep24-10, 12:26 AM
P: 2
Thanks a million berkeman, I think I got it all figured out!


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