The document describes the instruction set of the 8085 microprocessor, which is divided into 5 groups: data transfer, arithmetic, logical, branching/loop, and stack/machine control. It provides details of 20 representative instructions - 10 arithmetic instructions like ADD, SUB, and DAA and 10 data manipulation instructions like INR, DCR, and INX. For each instruction, it explains the operation, number of bytes, flags affected, and provides an example to illustrate how it works.

1. Prashant Sharma, Lecturer, ET&T, MMGGP, Rajnandgaon (C.G.) Page 1
Instruction Set of 8085 microprocessor
a) Data Transfer Group
b) Arithmetic Group
c) Logical Group
d) Branching/Loop Group
e) Stack and Machine Control Group
Notation used in Instruction and opcode
Notations Meaning
M Memory location pointed by HL register pair
R 8-bit register
RP 16-bit register pair
RS Source register
RD Destination register
Addr 16-bit address
X 8-bit data
b) Arithmetic Operation Group
1. ADD R 2. ADD M 3. ADC R 4. ADC M
5. ADI data 6. ACI data 7. DAD RP 8. SUB R
9. SUB M 10. SBB R 11. SBB M 12. SUI data
13. SBI data 14. DAA 15. INR R 16. INR M
17. DCR R 18. DCR M 19. INX RP 20. DCX RP
1. ADD R
Description - Add content of register R to accumulator A and store the result in
accumulator A.
Operation - A + R ----> A
No. of Bytes- 1
Flags - All flags are modified to reflect the result of addition.
Example - ADD C
Before Execution After Execution
C = 45H C = 45H
A = 35H A = 7A H

2. Prashant Sharma, Lecturer, ET&T, MMGGP, Rajnandgaon (C.G.) Page 2
2. ADD M
Description - Add content of memory location M to accumulator A and store
the result in accumulator A.
Operation - A + M ----> A OR A + (HL) ----> A
No. of Bytes- 1
Flags - All flags are modified to reflect the result of addition.
Example - ADD M
Before Execution After Execution
M = (HL) = (2030) = 30H M = (HL) = (2030) = 30H
A = 35H A = 65 H
3. ADC R
Description - Add content of register R and carry flag content to accumulator A
and store the result in accumulator A.
Operation - A + R + CY ----> A
No. of Bytes- 1
Flags - All flags are modified to reflect the result of addition.
Example - ADC B
Before Execution After Execution
B = 23H B = 23H
A = 35H A = 59 H
CY = 1 = Set CY = 0 = Reset
4. ADC M
Description - Add content of memory location M and carry flag content to
accumulator A and store the result in accumulator A.
Operation - A + M + CY ----> A OR A + (HL) + CY ----> A
No. of Bytes- 1
Flags - All flags are modified to reflect the result of addition.
Example - ADC M
Before Execution After Execution
M = (HL) = (1000) = 24H M = (HL) = (1000) = 24H
A = 32H A = 57 H
CY = 1 = Set CY = 0 = Reset

3. Prashant Sharma, Lecturer, ET&T, MMGGP, Rajnandgaon (C.G.) Page 3
5. ADI data
Description - Add immediate data to accumulator A and store the result in
accumulator A.
Operation - A + data ----> A
No. of Bytes- 2
Flags - All flags are modified to reflect the result of addition.
Example - ADI 73 H
Before Execution After Execution
data = 73H data = 73H
A = 35H A = A8 H
6. ACI data
Description - Add immediate data and carry flag content to accumulator A and
store the result in accumulator A.
Operation - A + data + CY ----> A
No. of Bytes- 2
Flags - All flags are modified to reflect the result of addition.
Example - ACI 10H
Before Execution After Execution
data = 10H data = 10H
A = 35H A = 46 H
CY = 1 = Set CY = 0 = Reset
7. DAD RP
Description - Add content of specified register pair RP to HL pair and store the
result in HL pair.
Operation - HL + RP ----> HL
No. of Bytes- 1
Flags - Only carry flags is modified to reflect the result of addition.
Example - DAD B
Before Execution After Execution
BC = 1245H BC = 1245H
HL = 1035H HL = 227A H

4. Prashant Sharma, Lecturer, ET&T, MMGGP, Rajnandgaon (C.G.) Page 4
8. SUB R
Description - Subtract content of register R from accumulator A and store the
result in accumulator A.
Operation - A - R ----> A
No. of Bytes- 1
Flags - All flags are modified to reflect the result of subtraction.
If CY = set, result is negative and is in 2’s complement form.
If CY = reset, result is positive and is in normal form.
Example - SUB C
Before Execution After Execution
(i) C = 35H C = 35H
A = 45H A = 10 H
A = 45 H 0100 0101
C = 35 H 0011 0101
2’s Complement of C ----> 1100 1011
A = 45 H 0100 0101
2’s Complement of C ----> + 1100 1011
1 0001 0000
Carry is generated so CY = set, microprocessor complement this carry so CY =
reset, which represent that the result is positive and is in normal form (0001
0000 = 10 H).
(ii) C = 45H C = 45H
A = 35H A = F0 H
A = 35 H 0011 0101
C = 45 H 0100 0101
2’s Complement of C ----> 1011 1011
A = 35 H 0011 0101
2’s Complement of C ----> + 1011 1011
1111 0000
No carry generated so CY = reset, microprocessor complement this carry so CY
= set, which represent that the result is negative and is in 2’s complement
form (1111 0000).
10H
F0H

5. Prashant Sharma, Lecturer, ET&T, MMGGP, Rajnandgaon (C.G.) Page 5
9. SUB M
Description - Subtract content of memory location M from accumulator A and
store the result in accumulator A.
Operation - A - M ----> A OR A - (HL) ----> A
No. of Bytes- 1
Flags - All flags are modified to reflect the result of subtraction.
If CY = set, result is negative and is in 2’s complement form.
If CY = reset, result is positive and is in normal form.
Example - SUB M
Before Execution After Execution
M = (HL) = (2030) = 30H M = (HL) = (2030) = 30H
A = 35H A = 05 H
Note: Subtraction method is same as SUB R.
10. SBB R
Description - Subtract content of register R and borrow flag content from
accumulator A and store the result in accumulator A.
Operation - A - R – Borrow Flag ----> A OR A - R – CY ----> A
No. of Bytes- 1
Flags - All flags are modified to reflect the result of subtraction.
If CY = set, result is negative and is in 2’s complement form.
If CY = reset, result is positive and is in normal form.
Example - SBB B
Before Execution After Execution
B = 23H B = 23H
A = 35H A =11 H
CY = 1 = Set CY = 0 = Reset
Note: Subtraction method is same as SUB R.

6. Prashant Sharma, Lecturer, ET&T, MMGGP, Rajnandgaon (C.G.) Page 6
11. SBB M
Description - Subtract content of memory location M and borrow flag content
from accumulator A and store the result in accumulator A.
Operation - A - M – Borrow Flag ----> A OR A - (HL) - CY ----> A
No. of Bytes- 1
Flags - All flags are modified to reflect the result of subtraction.
If CY = set, result is negative and is in 2’s complement form.
If CY = reset, result is positive and is in normal form.
Example - SBB M
Before Execution After Execution
M = (HL) = (1000) = 24H M = (HL) = (1000) = 24H
A = 32H A = 07 H
CY = 1 = Set CY = 0 = Reset
Note: Subtraction method is same as SUB R.
12. SUI data
Description - Subtract immediate data from accumulator A and store the result
in accumulator A.
Operation - A - data ----> A
No. of Bytes- 2
Flags - All flags are modified to reflect the result of subtraction.
If CY = set, result is negative and is in 2’s complement form.
If CY = reset, result is positive and is in normal form.
Example - ACI 10H
Before Execution After Execution
data = 10H data = 10H
A = 35H A = 25 H
Note: Subtraction method is same as SUB R.

7. Prashant Sharma, Lecturer, ET&T, MMGGP, Rajnandgaon (C.G.) Page 7
13. SBI data
Description - Subtract immediate data and borrow flag content from
accumulator A and store the result in accumulator A.
Operation - A – data – Borrow Flag ----> A OR A – data – CY ----> A
No. of Bytes- 2
Flags - All flags are modified to reflect the result of subtraction.
If CY = set, result is negative and is in 2’s complement form.
If CY = reset, result is positive and is in normal form.
Example - ACI 10H
Before Execution After Execution
data = 10H data = 10H
A = 35H A = 24 H
CY = 1 = Set CY = 0 = Reset
Note: Subtraction method is same as SUB R.
14. DAA (Decimal Adjust Accumulator)
Description - The contents of the accumulator A are changed from a binary
value to its equivalent two, 4-bit BCD number. This instruction is
used just after addition instruction.
Operation - A reg. in Binary ----> A reg. in BCD
No. of Bytes- 1
Flags - All flags are modified to reflect the result of addition. This is the
only instruction that uses auxiliary carry flag to perform the
operation of binary to BCD conversion.
Example - MVI A, 24H
ADI, 48H
DAA
Before Execution After Execution
data = 48H data = 48H
A = 24H A = 6C H (without DAA)
A = 72 H (with DAA)
A = 24H 0010 0100
data = 48H + 0100 1000
0110 1100 ----> 6C H
C is an invalid number in BCD so add 6H (0110) to make it valid.

8. Prashant Sharma, Lecturer, ET&T, MMGGP, Rajnandgaon (C.G.) Page 8
6C----> 0110 1100
+ 0110
0111 0010 ------> 72 H
Note: - DAA instruction checks the following:
(i) Is low order 4 bits D0-D3 greater than 9 or is AC flag is set. If any of the
above condition is satisfied then add 6 (0110) to low order 4 bits.
(ii) Is high order 4 bits D4-D7 greater than 9 or is CY flag is set. If any of the
above condition is satisfied then add 6 (0110) to high order 4 bits.
15. INR R
Description - Increment content of register R by one.
Operation - R + 1 ----> R
No. of Bytes- 1
Flags - Except carry flag, all other flags (S, Z, AC, and P) are modified to
reflect the result of operation.
Example - INR E
Before Execution After Execution
E = 45H E = 46H
16. INR M
Description - Increment content of memory location M by one.
Operation - M + 1 ----> M OR (HL) + 1 -----> (HL)
No. of Bytes- 1
Flags - Except carry flag, all other flags (S, Z, AC, and P) are modified to
reflect the result of operation.
Example - INR M
Before Execution After Execution
M = (HL) = (2000) = 45H M = (HL) = (2000) = 46H

9. Prashant Sharma, Lecturer, ET&T, MMGGP, Rajnandgaon (C.G.) Page 9
17. DCR R
Description - Decrement content of register R by one.
Operation - R - 1 ----> R
No. of Bytes- 1
Flags - Except carry flag, all other flags (S, Z, AC, and P) are modified to
reflect the result of operation.
Example - DCR E
Before Execution After Execution
E = 45H E = 44H
18. DCR M
Description - Decrement content of memory location M by one.
Operation - M - 1 ----> M OR (HL) - 1 -----> (HL)
No. of Bytes- 1
Flags - Except carry flag, all other flags (S, Z, AC, and P) are modified to
reflect the result of operation.
Example - DCR M
Before Execution After Execution
M = (HL) = (2000) = 45H M = (HL) = (2000) = 44H
19. INX RP
Description - Increment content of register pair RP by one.
Operation - RP + 1 ----> RP
No. of Bytes- 1
Flags - Except carry flag, all other flags (S, Z, AC, and P) are modified to
reflect the result of operation.
Example - INX H
Before Execution After Execution
HL = 1245H HL = 1246H
20. DCX RP
Description - Decrement content of register pair RP by one.
Operation - RP - 1 ----> RP
No. of Bytes- 1
Flags - Except carry flag, all other flags (S, Z, AC, and P) are modified to
reflect the result of operation.
Example - DCX H
Before Execution After Execution
HL = 1245H HL = 1244H