# LED combination display

Discussion in 'Homework Help' started by M.Rafay, May 6, 2012.

1. ### M.Rafay Thread Starter New Member

May 6, 2012
4
0
A combinational circuit is used to control a 6-segment LED (Light Emitting Diode) display of directional
and other symbols as shown below. (1000 represents the + sign, 1001 represents the - sign, 1010
represents a diamond and 1011 represents all segments illuminated). The circuit has four binary
inputs x1, x2, x3, and x4, and six binary outputs a, b, c, d, e and f. The string x3x2x1x0 represents
one of the 12 symbols. (For example, 0101 represents the direction SW.) The circuit works as follows.
If 0011 is input (representing the direction SE), then b = c = d = 1 indicating that the corresponding
segments are to be illuminated whereas a = e = f = 0 indicating these segments are to be darkened
(a) If 0100 is input (direction S), determine each of the following outputs.
1. a =
2. b =
3. c =
4. d =
5. e =
6. f =
(b) Complete the truth table for the output b. The truth table has 16 lines although some of them
will result in dont care conditions.
x3 x2 x1 x0 b
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0
1 0 0 1
1 0 1 0
1 0 1 1
1 1 0 0 X
1 1 0 1 X
1 1 1 0 X
1 1 1 1 X

Any help will be appreciated

2. ### R!f@@ AAC Fanatic!

Apr 2, 2009
8,791
771

Need more info mate.

3. ### t06afre AAC Fanatic!

May 11, 2009
5,939
1,222
The most easy way is set up a truth table which it looks like you most probably have done. Then draw a karnaugh diagram for each segment. This is a typical homework task. So let the OP have a try at it. Do not just serve the solution on a silver plate

4. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
Shown where? It's awfully hard to tell if you are on the right track if we can't see what you are working with.

You talk about inputs x1, x2, x3, x4 and then talk about a string x3x2x1x0. How do these relate to each other? Do they relate to each other? Where does this string come from? Are the x1, x2, and x3 the same in both? If so, what is x4 and x0?

5. ### M.Rafay Thread Starter New Member

May 6, 2012
4
0
Strings are used as a synonym here for the inputs
shown below means the examples which were given like the input 1000=+ ,1001=- etc

6. ### M.Rafay Thread Starter New Member

May 6, 2012
4
0
Yeah i have done the question with the way you mentioned. Thanks for the suggestion

7. ### M.Rafay Thread Starter New Member

May 6, 2012
4
0
it will be the answer if more info is give

8. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
But you state that the inputs are x1 through x4. But the string is made up of x0 through x3. Hence, you are specifying something (x0) in the string that is not one of the inputs and specifying an input (x4) that is not in the string. Now, I have a pretty good idea what you mean, but engineering is not about guessing.

Saying that 1000 should display the '+' symbol is fine, but unless we know what the inputs to the 6-segment LED display need to be in order to display the '+' symbol, we can't even begin to determine if what you have done is correct or not.