Instruction set

Instruction Set of 8085 µP

Compiled by:Parthesh Mankodi, Assistant Professor,

Department of Electronics & Communication

April 17, 2023 140701: Microprocessor & Interfacing 1

What is Instruction ?????

An instruction is a binary pattern designed inside a microprocessor to perform a specific function.

8085 has 246 instructions.

Each instruction is represented by an 8-bit binary value.

Classification Of Instructions

There are 5 Types,

(1) Data Transfer Instruction,(2) Arithmetic Instructions,(3) Logical Instructions,(4) Branching Instructions,(5) Control Instructions,

(1) Data Transfer Instructions

MOV Rd, RsMOV M, RsMOV Rd, MThis instruction copies the contents of the source register into the destination register.The contents of the source register are not altered.Example: MOV B,A or MOV M,B or MOV C,M

A 20 B 20

B 30 C

H 20 L 50

A 20 B

BEFORE EXECUTION AFTER EXECUTION

MOV B,A

B 30 C

H 20 L 50

B C 40

H 20 L 50

MOV M,B

MOV C,M40 40

MVI R, Data(8-bit)MVI M, Data(8-bit)

The 8-bit immediate data is stored in the destination register (R) or memory (M), R is general purpose 8 bit register such as A,B,C,D,E,H and L.

Example: MVI B, 60H or MVI M, 40HApril 17, 2023 140701: Microprocessor & Interfacing 6

B 60 C

AFTER EXECUTIONBEFORE EXECUTION

MVI B,60H

40HL=2050H

204FH 204FH

HL=2050H

MVI M,40H

LDA 16-bit address

The contents of a memory location, specified by a 16-bit address in the operand, are copied to the accumulator (A).The contents of the source are not altered.

Example: LDA 2000HApril 17, 2023 140701: Microprocessor & Interfacing 8

LDA 2000H2000H 2000H

LDAX Register PairLoad accumulator (A) with the contents of memory location whose address is specified by BC or DE or register pair.The contents of either the register pair or the memory location are not altered.

Example: LDAX D

LDAX D

STA 16-bit address

The contents of accumulator are copied into the memory location i.e. address specified by the operand in the instruction.

Example: STA 2000 H

A 50 A 50

STA 2000H2000H 2000H

STAX Register Pair

Store the contents of accumulator (A) into the memory location whose address is specified by BC Or DE register pair.

Example: STAX B

STAX B

1020H 1020H

SHLD 16-bit address

Store H-L register pair in memory. The contents of register L are stored into memory location specified by the 16-bit address.The contents of register H are stored into the next memory location.

Example: SHLD 2500 H

H 30 L 60

SHLD 2500H

2500H 2500H

The contents of register H are exchanged with the contents of register D.The contents of register L are exchanged with the contents of register E.Example: XCHG

D 20 E 40

H 70 L 80

D 70 E 80

H 20 L 40

Move data from H-L pair to the Stack Pointer (SP)This instruction loads the contents of H-L pair into SP.

Example: SPHL

H 25 L 00

BEFORE EXECUTION

AFTER EXECUTION

H 25 L 00

SP 2500

XTHLExchange H–L with top of stackThe contents of L register are exchanged with the location pointed out by the contents of the SP.The contents of H register are exchanged with the next location (SP + 1).

Example: XTHLApril 17, 2023 140701: Microprocessor & Interfacing 22

SP 2700

BEFORE EXECUTION

SP 2700

AFTER EXECUTION

L=SPH=(SP+1)

Load program counter with H-L contentsThe contents of registers H and L are copied into the program counter (PC).The contents of H are placed as the high-order byte and the contents of L as the low-order byte.

Example: PCHL

PC 6000

IN 8-bit port address

Copy data to accumulator from a port with 8-bit address.The contents of I/O port are copied into accumulator.

Example: IN 80 H

10 A 10

BEFORE EXECUTION

AFTER EXECUTION

IN 80H

PORT 80H

OUT 8-bit port address

Copy data from accumulator to a port with 8-bit addressThe contents of accumulator are copied into the I/O port.

Example: OUT 50 H

10 A 40

40 A 40

BEFORE EXECUTION

AFTER EXECUTION

OUT 50H

PORT 50H

Arithmetic Instructions

These instructions perform the operations like:

AdditionSubtractionIncrementDecrement

(1) Arithmetic Instructions

ADD R ADD M

The contents of register or memory are added to the contents of accumulator.The result is stored in accumulator.If the operand is memory location, its address is specified by H-L pair.

Example: ADD C or ADD MApril 17, 2023 140701: Microprocessor & Interfacing 31

B C 30

H 20 L 50

A 50A 20

ADD C A=A+R

ADD MA=A+M10 10

2050 2050

ADC RADC M

The contents of register or memory and Carry Flag (CY) are added to the contents of accumulator.The result is stored in accumulator.If the operand is memory location, its address is specified by H-L pair. All flags are modified to reflect the result of the addition.

Example: ADC C or ADC M

B C 20

ADC CA=A+R+CY

CY 1 CY 0

A 20 A 51

H 20 L 50 H 20 L 50

ADC MA=A+M+CY

30 302050H 2050H

ADI 8-bit data

The 8-bit data is added to the contents of accumulator.The result is stored in accumulator.

Example: ADI 10 H

A 50 A 60

ADI 10HA=A+DATA(8)

ACI 8-bit data

The 8-bit data and the Carry Flag (CY) are added to the contents of accumulator.The result is stored in accumulator.

Example: ACI 20 H

CY 1 CY 0

A 30 A 51

ACI 20HA=A+DATA(8)+CY

DAD Register pair

The 16-bit contents of the register pair are added to the contents of H-L pair.The result is stored in H-L pair.If the result is larger than 16 bits, then CY is set.

Example: DAD D

D 10 E 20

H 20 L 50

D 10 E 20

H 30 L 70

CY 0 CY 0

DAD DHL=HL+R

SUB RSUB M

The contents of the register or memory location are subtracted from the contents of the accumulator.The result is stored in accumulator.If the operand is memory location, its address is specified by H-L pair.

Example: SUB B or SUB MApril 17, 2023 140701: Microprocessor & Interfacing 41

B 30 C

SUB BA=A-R

A 50 A 40

SUB M A=A-M

10 101020H1020H

SBB RSBB M

The contents of the register or memory location and Borrow Flag (i.e.CY) are subtracted from the contents of the accumulator.The result is stored in accumulator. If the operand is memory location, its address is specified by H-L pair.

Example: SBB C or SBB M

B C 20

SBB CA=A-R-CY

SBB MA=A-M-CY

10 102050H 2050H

SUI 8-bit data

OPERATION: A=A-DATA(8)The 8-bit immediate data is subtracted from the contents of the accumulator.The result is stored in accumulator.

Example: SUI 45 HApril 17, 2023 140701: Microprocessor & Interfacing 45

SBI 8-bit data

The 8-bit data and the Borrow Flag (i.e. CY) is subtracted from the contents of the accumulator.The result is stored in accumulator.

Example: SBI 20 H

A 29SBI 20HA=A-DATA(8)-CY

INR RINR M

The contents of register or memory location are incremented by 1.The result is stored in the same place.If the operand is a memory location, its address is specified by the contents of H-L pair.

Example: INR B or INR MApril 17, 2023 140701: Microprocessor & Interfacing 48

B 10 C

B 11 C

AFTER EXECUTION

30 312050H

INR MM=M+1

B 10 C

BEFORE EXECUTION

INR BR=R+1

INX Rp

The contents of register pair are incremented by 1.The result is stored in the same place.

Example: INX HApril 17, 2023 140701: Microprocessor & Interfacing 50

H 10 L 20

H 10 L 21

INX HRP=RP+1

DCR RDCR M

The contents of register or memory location are decremented by 1.The result is stored in the same place.If the operand is a memory location, its address is specified by the contents of H-L pair.Example: DCR E or DCR M

D E 19

AFTER EXECUTION

D E 20

BEFORE EXECUTION

DCR ER=R-1

21 202050H

DCR MM=M-1

DCX Rp

The contents of register pair are decremented by 1.The result is stored in the same place.

Example: DCX DApril 17, 2023 140701: Microprocessor & Interfacing 54

D 10 E 20

D 10 E 19

DCX DRP=RP-1

(1) Logical Instructions

ANA RANA M

AND specified data in register or memory with accumulator.Store the result in accumulator (A).

Example: ANA B, ANA MApril 17, 2023 140701: Microprocessor & Interfacing 56

B 10 C

B 0F C

AFTER EXECUTION

ANA BA=A and R

B 0F C

BEFORE EXECUTION

A 11A 55

B3 B32050H

ANA MA=A and M

1010 1010=AAH0000 1111=0FH

0000 1010=0AH

0101 0101=55H1011 0011=B3H

0001 0001=11H

ANI 8-bit data

AND 8-bit data with accumulator (A).Store the result in accumulator (A)

Example: ANI 3FH

ANI 3FHA=A and DATA(8)

1011 0011=B3H0011 1111=3FH

0011 0011=33H

XRA Register (8-bit)

XOR specified register with accumulator.Store the result in accumulator.

Example: XRA C

B 10 C

B C 2D

AFTER EXECUTION

XRA CA=A xor R

B C 2D

BEFORE EXECUTION

1010 1010=AAH0010 1101=2DH

1000 0111=87H

XOR data in memory (memory location pointed by H-L pair) with Accumulator.Store the result in Accumulator.

Example: XRA MApril 17, 2023 140701: Microprocessor & Interfacing 62

H 20 L 50

AFTER EXECUTION

XRA MA=A xor M

BEFORE EXECUTION

0101 0101=55H1011 0011=B3H

1110 0110=E6H

H 20 L 50

A E6B3 B32050H 2050H

XRI 8-bit data

XOR 8-bit immediate data with accumulator (A).Store the result in accumulator.

Example: XRI 39H

XRI 39HA=A xor DATA(8)

1011 0011=B3H0011 1001=39H

1000 1010=8AH

ORA RegisterOR specified register with accumulator (A).Store the result in accumulator.

Example: ORA B

ORA BA=A or R

1010 1010=AAH0001 0010=12H

1011 1010=BAH

B 12 C

OR specified register with accumulator (A).Store the result in accumulator.

Example: ORA M

ORA MA=A or M

0101 0101=55H1011 0011=B3H

1111 0111=F7H

H 20 L 50

A 55 A F7

H 20 L 50

B3 B32050H 2050H

ORI 8-bit data

OR 8-bit data with accumulator (A).Store the result in accumulator.

Example: ORI 08H

ORI 08HA=A or DATA(8)

1011 0011=B3H0000 1000=08H

1011 1011=BBH

CMP RegisterCMP M

Compare specified data in register or memory with accumulator (A).Store the result in accumulator.

Example: CMP D or CMP MApril 17, 2023 140701: Microprocessor & Interfacing 72

B 10 C

D B9 E

AFTER EXECUTION

CMP DA-R

D B9 E

BEFORE EXECUTION

A B8A B8

B8 B82050H CMP M

A>R: CY=0,Z=0A=R: CY=0,Z=1A<R: CY=1,Z=0

A>M: CY=0,Z=0A=M: CY=0,Z=1A<M: CY=1,Z=0

CPI 8-bit data

Compare 8-bit immediate data with accumulator (A).Store the result in accumulator.

Example: CPI 30H

CPI 30HA-DATA

A>DATA: CY=0,Z=0A=DATA: CY=0,Z=1A<DATA: CY=1,Z=0

1011 1010=BAH

It sets the carry flag to 1.Example: STC

CY 1STCCY=1

It complements the carry flag.Example: CMC

It complements each bit of the accumulator.Example: CMA

Rotate accumulator leftEach binary bit of the accumulator is rotated left by one position.Bit D7 is placed in the position of D0 as well as in the Carry flag.CY is modified according to bit D7.

Example: RLC.April 17, 2023 140701: Microprocessor & Interfacing 81

B7 B6 B5 B4 B3 B2 B1 B0CY

B6 B5 B4 B3 B2 B1 B0 B7B7

AFTER EXECUTION

BEFORE EXECUTION

Rotate accumulator rightEach binary bit of the accumulator is rotated right by one position.Bit D0 is placed in the position of D7 as well as in the Carry flag.CY is modified according to bit D0.

Example: RRC.

B7 B6 B5 B4 B3 B2 B1 B0 CY

B0 B7 B6 B5 B4 B3 B2 B1 B0

AFTER EXECUTION

BEFORE EXECUTION

Rotate accumulator left through carryEach binary bit of the accumulator is rotated left by one position through the Carry flag.Bit D7 is placed in the Carry flag, and the Carry flag is placed in the least significant position D0.CY is modified according to bit D7.

Example: RAL.April 17, 2023 140701: Microprocessor & Interfacing 85

B7 B6 B5 B4 B3 B2 B1 B0CY

B6 B5 B4 B3 B2 B1 B0 CYB7

AFTER EXECUTION

BEFORE EXECUTION

Rotate accumulator right through carryEach binary bit of the accumulator is rotated left by one position through the Carry flag.Bit D7 is placed in the Carry flag, and the Carry flag is placed in the least significant position D0.CY is modified according to bit D7.

Example: RAR

B7 B6 B5 B4 B3 B2 B1 B0 CY

CY B7 B6 B5 B4 B3 B2 B1 B0

AFTER EXECUTION

BEFORE EXECUTION

Concept of Subroutine

In 8085 microprocessor a subroutine is a separate program written aside from main program ,this program is basically the program which requires to be executed several times in the main program. The microprocessor can call subroutine any time using CALL instruction. after the subroutine is executed the subroutine hands over the program to main program using RET instruction.

Branching Instructions

The branch group instructions allows the microprocessor to change the sequence of program either conditionally or under certain test conditions. The group includes,(1) Jump instructions,(2) Call and Return instructions,(3) Restart instructions,

(1) Branching Instructions

JUMP ADDRESS

Jump unconditionally to the address.The instruction loads the PC with the address given within the instruction and resumes the program execution from specified location.Example: JMP 2000H

PC PC 2000JMP 2000H

Conditional JumpsInstruction Code

Decription Condition For Jump

JC Jump on carry CY=1

JNC Jump on not carry CY=0

JP Jump on positive S=0

JM Jump on minus S=1

JPE Jump on parity even P=1

JPO Jump on parity odd P=0

JZ Jump on zero Z=1

JNZ Jump on not zero Z=0

CALL address

Call unconditionally a subroutine whose starting address given within the instruction and used to transfer program control to a subprogram or subroutine.

Example: CALL 2000H

Conditional Calls

Instruction Code Description Condition for CALL

CC Call on carry CY=1

CNC Call on not carry CY=0

CP Call on positive S=0

CM Call on minus S=1

CPE Call on parity even P=1

CPO Call on parity odd P=0

CZ Call on zero Z=1

CNZ Call on not zero Z=0

Return from the subroutine unconditionally.This instruction takes return address from the stack and loads the program counter with this address.

Example: RETApril 17, 2023 140701: Microprocessor & Interfacing 95

SP 27FD

SP 27FF

PC 6200

RET27FFH

Restart n (0 to 7)This instruction transfers the program control to a specific memory address. The processor multiplies the RST number by 8 to calculate the vector address.

Example: RST 6

SP 3000

PC 2000

SP 2999

PC 003001

ADDRESS OF THE NEXT INSTRUCTION IS 2001H

Vector Address For Return Instructions

Instruction Code Vector Address

RST 0 0*8=0000H

RST 1 0*8=0008H

RST 2 0*8=0010H

RST 3 0*8=0018H

RST 4 0*8=0020H

RST 5 0*8=0028H

RST 6 0*8=0030H

Rst 7 0*8=0038H

(1) Control Instructions

No operationNo operation is performed.The instruction is fetched and decoded but no operation is executed.

Example: NOPApril 17, 2023 140701: Microprocessor & Interfacing 100

HaltThe CPU finishes executing the current instruction and halts any further execution.An interrupt or reset is necessary to exit from the halt state.

Example: HLT

Read Interrupt MaskThis is a multipurpose instruction used to read the status of interrupts 7.5, 6.5, 5.5 and read serial data input bit.The instruction loads eight bits in the accumulator with the following interpretations.

Example: RIM

RIM Instruction

Set Interrupt MaskThis is a multipurpose instruction and used to implement the 8085 interrupts 7.5, 6.5, 5.5, and serial data output.The instruction interprets the accumulator contents as follows.

Example: SIMApril 17, 2023 140701: Microprocessor & Interfacing 104

SIM Instruction

Instruction set

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