Digital Logic and Truth Tables

Electronics and Embedded Systems · CHAPTER 1 / 5

Level: introductory undergraduate · Study session: 15–20 minutes including practice.

Learning outcome: Translate Boolean rules into reproducible input-output behaviour.

Before you begin: Basic algebra, SI units and a willingness to sketch the problem.

1. Understand the idea

A logic signal represents a discrete state within a specified voltage range. AND requires all inputs high; OR requires at least one high; NOT reverses a state. A truth table enumerates possible inputs and is a useful test specification before writing firmware or wiring a circuit.

2. Write the model

YAND = A·B; YOR = A+B; YNOT = ¬A

Define the symbols from the worked case before substituting values. Keep units consistent, record the assumptions and round only after the calculation.

3. Follow a worked example

For an alarm that needs enable E and fault F, Y=E AND F. A fault with enable=0 does not trigger this Boolean alarm; that design choice must be assessed against the actual safety requirement.

4. Explore the model

Figure: calculated teaching cases; straight segments connect sampled points, not experimental observations. Read exact values below.

Illustrative scenario sweep — synthetic educational data
Enable E	Fault F	Alarm Y
0	0	0
0	1	0
1	0	0
1	1	1

Enumerate all four binary pairs. Compare the AND result with OR and explain the difference.

5. Reproduce it yourself

Copy the input cases into Excel or a notebook and name each quantity and unit.
Recalculate each result from the stated equation or rule. For qualitative cases, explain the state or partition decision instead.
Change one input, predict the direction of change, then calculate again.
Write one sentence explaining where the model stops being valid.

6. Check your understanding

For A=0 and B=1, what are AND and OR?

Reveal the answer and check your work

AND=0; OR=1.

Compare your result, units and reasoning. If they differ, return to the equation and test the worked case first.

7. Common mistake

A Boolean safety example is not a certified safety circuit.

Further study and academic note

Explore the discipline reference and further learning resources. This is an original IIMEEE introductory teaching note with synthetic examples; it is not a peer-reviewed research result or a professional design specification. Figures were constructed from the listed teaching cases. Resource links support further study and do not imply endorsement.