Question

2. The decimal digits 0 to 9 are represented by four logic signals using the 7321 weighted BCD code. Only the code 0011 is used to represent the digit 3. In addition the code 1100 is used to represent the character E. Codes that do not represent either a decimal digit (including 0100), or the character E never occur. The logic signals are inputs to a decoder circuit whose outputs provide drive signals for a seven segment display system shown in Figure Q2.1. The segments are selected so as to represent the shape of each digit/character as defined in Figure Q2.2 where the lightly shaded segments for digits 6 and 9 may be either ON or OFF for those digits. When a circuit output is logic 1, the segment it drives is ON (visible) Draw a truth table for all the seven segments. 15 a) Find the simplest Boolean expression for the outputs that connect to segments dand Draw one circuit diagram for the decoder for both segments d and g taking advantage of any common AND terms to reduce the complexity of the circuit b) Find the simplest Boolean expressions for the outputs, a, b, c,e and f 10 A circuit diagram is not needed Figure 02.1 0008858009 8 Figure 02.2 Total 25

Answer 1

Solution:

Whenever the logic(a,b,c,d,e,f,g) are high the LED lits up.

Truth table

a b Cd e f g АЗ АГА! АО 0 0 0 1 01 1 00 0 0 0 0 1 0 1 1 0 1 1 01 0 1 01 0 1 1 0 0 1 1

ad d 0

An* A3ん lo lo