# Digital System Design - Decoder Question.

Discussion in 'Homework Help' started by essedra, Nov 19, 2009.

Not open for further replies.
1. ### essedra Thread Starter New Member

Nov 19, 2009
5
0
This is the text and the schema of the question....I need help, really desperate....don't know what to do...Appreciate any responses...

2. ### Papabravo Expert

Feb 24, 2006
10,340
1,850
You would start with the truth table which is supposed to be 16 x 11. The 16 rows correspond to the 16 possible hexadecimal digits in the set:

$
\ \ \ \ \left\{0,\ 1,\ 2,\ 3,\ 4,\ 5,\ 6,\ 7,\ 8,\ 9,\ A,\ B,\ C,\ D,\ E,\ F\right\}
$

Each of those 16 elements can be represented by 4 binary digits. Corressponding to each row will be 7 bits that represent weather the segments for that hexadecimal digit will be on or off. The first three rows of the table are given in the problem statement.

When the table is done you can write 7 boolean expressions, one for each segment. Then you have to optimize those expressions, and you will be mostly done. So sixteen rows with 4 + 7 = 11 columns. Hint: Draw a double vertical line between the 4 input columns and the 7 output columns.