This document discusses arithmetic operations on the MCS-51 microprocessor, including addition, subtraction, multiplication, division, increment, decrement, and decimal adjustment. It provides examples of performing these operations on decimal, hexadecimal, and binary numbers. It also describes the instructions used for each operation and how results are stored, particularly noting that addition and subtraction affect the carry flag. Code samples are given for addition, subtraction, and multiplication operations. Homework assignments are provided to write programs for additional and multiplication operations.

1. MCS-51 Arithmetic Operation
Microprocessor
(MCS-51)

2. Number Comparison table
Decimal Hexadecimal Binary
0 0 0 0 0 0
1 1 0 0 0 1
2 2 0 0 1 0
3 3 0 0 1 1
4 4 0 1 0 0
5 5 0 1 0 1
6 6 0 1 1 0
7 7 0 1 1 1
8 8 1 0 0 0
9 9 1 0 0 1
1 0 A 1 0 1 0
1 1 B 1 0 1 1
1 2 C 1 1 0 0
1 3 D 1 1 0 1
1 4 E 1 1 1 0
1 5 F 1 1 1 1
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3. MCS-51 is 8-bits word size
Microcontroller
• MCS-51 is 8-bits word size computer
1 1 0 1 0 0 1 1
D 3
Binary
Hexadecimal
8 Bits = 1 Byte
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4. Arithmetic operation
• Additional
• Subtraction
• Multiplication
• Division
• Increment
• Decrement
• Decimal Adjustment (to BCD)
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5. Additional Review
• Decimal
1
3 4 +
9 4
1 2 8
1
9 +
9
1 8
• Hexadecimal
0
B 4 +
1 4
C 8
1
F +
F
1 E
1
F F +
0 1
1 0 0
1
F F +
F F
1 F E
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Additional
MSB
One Byte
Answer

6. MCS-51 Additional Operation
• Law of operation with Assembly
– The First operand MUST be Acc
– Every additional operation, the Result will store in
• Carry flag (as Most Significant bit)
• Acc
– Every Additional will effect to Carry flag
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7. Additional Instructions
– Instructions
• ADD A, Rn
• ADD A, #X
• ADD A, Rx
• ADD A, @Ri
• ADDC A, Rn
• ADDC A, #X
• ADDC A, Rx
• ADDC A, @Ri
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8. Sample Additional (Small number)
• A =
+
• R3 =
• ADD A, R3
• C = = Acc
8 C
3 8
C 40
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9. Sample Additional (Big number)
• A =
+
• R3 =
• ADD A, R3
• C = = Acc
A 7
B 3
5 A1
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10. Simple Additional Program
• See Handout Chapter 8
• Example 0:
• Program to summation R0 and R1, then
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11. Sample “16-bits Additional Program”
• “16-bits Additional Program”
– Such as: 1001100110111011+ 99BB+
1101110010111011 DCBB
1 0111011001110110 1 76 76
• Solution:
– Because the word size of MCS-51 is 8-bits, the
diagram able to draw as below.
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12. Sample “16-bits Additional Program”
9 9 B B
D C 6 4
x x x x
R1 R2
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P2 P1
x x
ORG 00H
MOV A, R2
ADD A, P1 ; C, Acc
MOV 12h, A
MOV A, R1
ADDC A, P2 ; C, Acc
MOV 11h, Acc
CLR A
MOV Acc.0, C
MOV 10h, Acc
END
10h 11h 12h
01 76 1F

13. MCS-51 Subtraction Operation
• Law of operation
– Every Subtraction will include Carry flag
– Result will store in Acc
– Result on Carry flag
• “0” on Carry flag represent Positive result in Acc
• “1” on Carry flag represent Negative result in Acc
– Negative number result will be show in a Second
complement format
– Every Subtraction will effect to Carry flag
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14. Subtraction Review
• Decimal
3 4 -
1 2
2 2
5 +
9
- 4
• Hexadecimal
B 4 -
1 4
C 8
1 C -
1 E
F E
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Borrow (C) = 1
FE = 2 Complement of -2

15. Mathematic on Binary System
• Normal
5 -
7
-2
+ 4
2
• Binary System
0 5 -
0 7
F E
+ 0 4
0 2
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FE = 2’n Complement of -2
Borrow (C) = 1

16. Subtraction Instruction
– Instructions
• SUBB A, Rn
• SUBB A, #X
• SUBB A, Rx
• SUBB A, @Ri
• Note: Every Additional will effect to Carry flag
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17. 32 bits Subtraction Program
• _
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9 9 7 A
1 C 9 4
x x x x
11h 12h
21h 22h
9 D B B
D 3 6 4
13h 14h
x x x x
23h 24h
R1 R2 R3 R4
ORG 00H
CLR C
MOV A, R4
SUBB A, 14h
MOV 24h, A
MOV A, R3
SUBB A, 13h
MOV 23h, Acc
MOV A, R2
SUBB A, 12h
MOV 22h, Acc
MOV A, R1
SUBB A, 11h
MOV 21h, Acc
END

18. Test in Assembly Editor and Emulator
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19. Assignment 1
• Chapter 8, Example 2
– Complete the Example 2 then check your code in the
Laboratory
– Check and Sign by Instructor
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21. Homework 2
• Chapter 8,
– Refer to Example 3
– Write diagram and assembly code for MCS-51 to process
“32bits additional program”
– Specify data enter location by yourself.
– Generate Test data by your self (if needed)
– Submit before next class start.
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22. Multiplication Operation
• Only operate by Register Acc and B
• Answer
– Low Byte store in Acc
– High Byte store in B
• Instruction
– MUL AB
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3 E
9 2
x xy y
x

23. Sample Multiplication Operation
Basic Multiplication
See Handout Chapter 8
Example 1
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3 E
9 2
x xy y
x

24. Sample Multiplication Operation
16-bits multiplication:
See Handout Chapter 8
Example 4
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3 E
9 2 x
9 29 2
9 29 2
9 29 2
9 29 2
9 29 2 9 29 2

25. Division Operation
• Operate by register Acc and B
– Acc / B
• Answer
– Answer store in Acc
– Fraction store in B
• Instruction
– DIV AB
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3 E0 5

26. Assignment 2
• Perform write program for MCS51 to operate
“16-bits Multiplication”
• Check by Instructor
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27. Sample Division Operation
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3 E0 5
0 C
3 C
0 2
C 2
5

28. Increment
• Increase by One
• On Over flow (Increase FF) will return to 00
• Effect to Carry flag?
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29. Decrement
• Decrease by One
• On Over flow (Decrease 00) will return to FF
• Effect to Carry flag?
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30. Binary Coded Decimal (BCD)
• Decimal Adjustment Acc
– DA A
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31. Homework 3
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