1. Basic Digital Logic: X-OR and X-NOR Gates
©Paul Godin
Created September 2007
Last update Sept 2009

2. Specialized Gates
Some instances in digital logic require specialized logic and gates.
This section discusses these basic gates.

3. Equality and Difference
Some circuits need to compare two digital values and report if they are equal or different. Examples include digital alarm clocks, digital addition, communications and control systems.
Logic gates are needed to provide one output if both inputs are the same and another output if both inputs are different. 1 1 1
Equal
Different

4. X-OR and X-NOR Input Status A B = Y A B = Y Same Different Different
Output 1
Input
Output 1
Same
Different
Different
Same
A B = Y
A B = Y
These devices act as OR and NOR gates, with an “exclusivity” when both inputs are 1.

5. Comparator Exercise 1
1st value
2nd value 1 1 1 1

6. Comparator Exercise 2
1st value
2nd value 1 1 1

7. Comparator Exercise 3
1st value
2nd value 1 1 1 1

8. Comparator Exercise 4
1st value
2nd value 1 1 1

9. Invert Exercise 5
X-OR and X-NOR gates can be used to invert or not invert a signal. Demonstrate and describe this principle.

10. Buffers
Digital devices need to deal with the electrical aspect of interconnectivity such as voltage and current.
Sensitive digital circuits need protection from static discharge, short circuits and other external factors.
Buffers and Drivers are devices that ensure there is a good electrical interface with other circuits while reducing the risk of damage to sensitive digital circuitry.

11. Buffers and Drivers
Buffers and Drivers are used for electrical reasons and may not affect the logic state.
Note these devices don’t affect the logic value.

12. END
©Paul R. Godin
gmail.com