1. Software Developers
View of Hardware
Electronic Circuits

2. What are circuits?
 Computers are electrical devices, so
therefore all functions performed by a
computer need to done via the use of circuits.
 Circuits are designed via the use of Logic
Gates which show the path and the way in
which electronic signals are sent and
received.

3. Logic Gates
 Are a hardware circuit that produces a 0 or 1,
which is normally an electronic impulse.
 There are THREE basic logic gates and
THREE extended gates that can be used to
build integrated circuits.

4. BASIC GATES
1. NOT Gate
 This is the simplest of all gates, it involves a
single input and a single output.
 The purpose of this gate is the flipping of a bit
similar to what is performed in one’s
complement.

5. NOT Gate
A X
0 1

6. NOT Gate

7. NOT Gate

8. NOT Gate – Truth Table
IF A = 0 THEN
A X
X=1
0 1 ELSE
X=0
1 0 ENDIF

9. BASIC GATES
1. AND Gate
 This is involves two inputs to produce one
output.
 Both inputs must be true for the output to be true.

10. AND Gate
A
X
B

11. AND Gate

12. AND Gate

13. AND Gate

14. AND Gate – Truth Table
A B X IF A=1 AND B=1THEN
0 0 0 X=1
0 1 0
ELSE
X=0
1 0 0
ENDIF
1 1 1

15. BASIC GATES
1. OR Gate
 This is involves two inputs to produce one
output.
 If either inputs are true then the output will be
true.

16. OR Gate
A
X
B

17. OR Gate

18. OR Gate

19. OR Gate

20. OR Gate

21. OR Gate – Truth Table
A B X IF A=1 OR B=1THEN
0 0 0 X=1
0 1 1
ELSE
X=0
1 0 1
ENDIF
1 1 1

22. Activity 1
Complete the truth table for the following circuit.
A
X
Y
B

23. Truth Table
A B X Y
0 0
0 1
1 0
1 1

24. EXTENDED GATES
1. NAND Gate
 This is involves two inputs to produce one
output.
 The output is the opposite of an AND gate.
 Is a combination of an AND and NOT gate.

25. NAND Gate
A
X
B

26. NAND Gate – Truth Table
A B X IF A=1 AND B=1THEN
0 0 1 X=0
0 1 1
ELSE
X=1
1 0 1
ENDIF
1 1 0

27. EXTENDED GATES
1. NOR Gate
 This is involves two inputs to produce one
output.
 The output is the opposite of an OR gate.
 It is a combination of an OR and NOT.

28. NOR Gate
A
X
B

29. NOR Gate – Truth Table
A B X IF A=1 AND B=1THEN
0 0 1 X=0
0 1 0
ELSE
X=1
1 0 0
ENDIF
1 1 0

30. EXTENDED GATES
1. XOR Gate
 This stands for exclusive OR.
 This gate is true if only one input is true.

31. XOR Gate
A
X
B

32. XOR Gate – Truth Table
A B X
0 0 0
0 1 1
1 0 1
1 1 0

33. SPECIALITY CIRCUITS
 Designed to make use of our binary
knowledge and our circuitry knowledge
 Examples include:
 Adders
 Flip Flops
 Shifts

34. DESIGNING SPECIALITY
CIRCUITS
 These circuits are written to provide a specific
function:
 Adder (Binary Addition)
 Flip Flop (Binary Storage)

35. DESIGNING SPECIALITY
CIRCUITS
 Follow these steps:
 Identify inputs and outputs
 Identify the components required to produce the
output (AND, OR, NOT, NAND, NOR, XOR)
 Construct the solution with logic gates
 Check the solution for validity (with a truth table)
 Evaluate the circuit design (could you make this
circuit better by chaining different logic gates)

36. Binary Half Adder
 This device is basically a calculator.
 Lets look at the half adder truth table first.

37. Binary Half Adders
INPUT OUTPUT
 To create a
Binary Adder, A B Carry Sum
we need to find
a logic gate that
give us the 0 0 0 0
Carry output
and a logic gate
0 1 0 1
the Sum output
1 0 0 1
1 1 1 0

38. Binary Half Adders
INPUT OUTPUT
 Carry output is
created using a A B Carry Sum
AND logic gate
0 0 0 0
A
X
B 0 1 0 1
1 0 0 1
1 1 1 0

39. Binary Half Adders
INPUT OUTPUT
 Sum output is
created using a A B Carry Sum
XOR logic gate
0 0 0 0
A
X
B
0 1 0 1
1 0 0 1
1 1 1 0

40. Binary Half Adders
The circuit:
A
Carry (C)
B
Sum (S)

41. Half And Full Adders
 Half Adders only work to add two digits
 To add more than 2 binary digits we need a full
adder
 A full adder allows us to add the “carry” value to
an binary addition

42. Full Adders
A
B
Carry
(C)
Sum (S)
Carry in

43. Truth Tables
Construct a truth table for the full adder.

44. Truth Table
A B CARRY CARRY SUM
IN
0 0 0 0 0
0 0 1 0 1
0 1 0 0 1
0 1 1 1 0
1 0 0 0 1
1 0 1 1 0
1 1 0 1 0
1 1 1 1 1

45. Circuit Design Steps
 Identify inputs and outputs.
A+B+C=X
 Identify the components needed to obtain
the desired output.
AND/OR/NOT/XOR/NAND/NOR
 Construct a truth table to test.

46. Activity 2
 Construct a truth table for the following
circuit.
A
Y
B X
C

47. A
B X
C
A B C Y X
0 0 0 1 1
0 0 1 1 0
0 1 0 1 1
0 1 1 1 0
1 0 0 1 1
1 0 1 1 0
1 1 0 0 0
1 1 1 0 1

48. Activity 3

49. Fault Door Switch x Light
0 0 0 0
0 0 1 0
0 1 0 0
0 1 1 1
1 0 0 0
1 0 1 0
1 1 0 0
1 1 1 0