8085 Instruction Set Instructions

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8085 Instruction Set Page 1

8085 INSTRUCTION SET

INSTRUCTION DETAILS

DATA TRANSFER INSTRUCTIONS

Opcode Operand Description

Copy from source to destination

MOV Rd, Rs This instruction copies the contents of the source

M, Rs register into the destination register; the contents of

Rd, M the source register are not altered. If one of the operands is a

memory location, its location is specified by the contents of

the HL registers.

Example: MOV B, C or MOV B, M

Move immediate 8-bit

MVI Rd, data The 8-bit data is stored in the destination register or

M, data memory. If the operand is a memory location, its location is

specified by the contents of the HL registers.

Example: MVI B, 57 or MVI M, 57

Load accumulator

LDA 16-bit address The contents of a memory location, specified by a

16-bit address in the operand, are copied to the accumulator.

The contents of the source are not altered.

Example: LDA 2034 or LDA XYZ

Load accumulator indirect

LDAX B/D Reg. pair The contents of the designated register pair point to a memory

location. This instruction copies the contents of that memory

location into the accumulator. The contents of either the

register pair or the memory location are not altered.

Example: LDAX B

Load register pair immediate

LXI Reg. pair, 16-bit data The instruction loads 16-bit data in the register pair

designated in the operand.

Example: LXI H, 2034

Load H and L registers direct

LHLD 16-bit address The instruction copies the contents of the memory location

pointed out by the 16-bit address into register L and copies

the contents of the next memory location into register H. The

contents of source memory locations are not altered.

Example: LHLD 2040

8085 Instruction Set Page 2

Store accumulator direct

STA 16-bit address The contents of the accumulator are copied into the memory

location specified by the operand. This is a 3-byte

instruction, the second byte specifies the low-order address

and the third byte specifies the high-order address.

Example: STA 4350 or STA XYZ

Store accumulator indirect

STAX Reg. pair The contents of the accumulator are copied into the memory

location specified by the contents of the operand (register

pair). The contents of the accumulator are not altered.

Example: STAX B

Store H and L registers direct

SHLD 16-bit address The contents of register L are stored into the memory location

specified by the 16-bit address in the operand and the contents

of H register are stored into the next memory location by

incrementing the operand. The contents of registers HL are

not altered. This is a 3-byte instruction, the second byte

specifies the low-order address and the third byte specifies the

high-order address.

Example: SHLD 2470

Exchange H and L with D and E

XCHG none The contents of register H are exchanged with the contents of

register D, and the contents of register L are exchanged with

the contents of register E.

Example: XCHG

Copy H and L registers to the stack pointer

SPHL none The instruction loads the contents of the H and L registers

into the stack pointer register, the contents of the H register

provide the high-order address and the contents of the L

register provide the low-order address. The contents of the H

and L registers are not altered.

Example: SPHL

Exchange H and L with top of stack

XTHL none The contents of the L register are exchanged with the stack

location pointed out by the contents of the stack pointer

register. The contents of the H register are exchanged with

the next stack location (SP+1); however, the contents of the

stack pointer register are not altered.

Example: XTHL

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Push register pair onto stack

PUSH Reg. pair The contents of the register pair designated in the operand are

copied onto the stack in the following sequence. The stack

pointer register is decremented and the contents of the high-

order register (B, D, H, A) are copied into that location. The

stack pointer register is decremented again and the contents of

the low-order register (C, E, L, flags) are copied to that

location.

Example: PUSH B or PUSH A

Pop off stack to register pair

POP Reg. pair The contents of the memory location pointed out by the stack

pointer register are copied to the low-order register (C, E, L,

status flags) of the operand. The stack pointer is incremented

by 1 and the contents of that memory location are copied to

the high-order register (B, D, H, A) of the operand. The stack

pointer register is again incremented by 1.

Example: POP H or POP A

Output data from accumulator to a port with 8-bit address

OUT 8-bit port address The contents of the accumulator are copied into the I/O port

specified by the operand.

Example: OUT 87

Input data to accumulator from a port with 8-bit address

IN 8-bit port address The contents of the input port designated in the operand are

read and loaded into the accumulator.

Example: IN 82

8085 Instruction Set Page 4

ARITHMETIC INSTRUCTIONS

Opcode Operand Description

Add register or memory to accumulator

ADD R The contents of the operand (register or memory) are

M added to the contents of the accumulator and the result is

stored in the accumulator. If the operand is a memory

location, its location is specified by the contents of the HL

registers. All flags are modified to reflect the result of the

addition.

Example: ADD B or ADD M

Add register to accumulator with carry

ADC R The contents of the operand (register or memory) and

M the Carry flag are added to the contents of the accumulator

and the result is stored in the accumulator. If the operand is a

memory location, its location is specified by the contents of

the HL registers. All flags are modified to reflect the result of

the addition.

Example: ADC B or ADC M

Add immediate to accumulator

ADI 8-bit data The 8-bit data (operand) is added to the contents of the

accumulator and the result is stored in the accumulator. All

flags are modified to reflect the result of the addition.

Example: ADI 45

Add immediate to accumulator with carry

ACI 8-bit data The 8-bit data (operand) and the Carry flag are added to the

contents of the accumulator and the result is stored in the

accumulator. All flags are modified to reflect the result of the

addition.

Example: ACI 45

Add register pair to H and L registers

DAD Reg. pair The 16-bit contents of the specified register pair are added to

the contents of the HL register and the sum is stored in the

HL register. The contents of the source register pair are not

altered. If the result is larger than 16 bits, the CY flag is set.

No other flags are affected.

Example: DAD H

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Subtract register or memory from accumulator

SUB R The contents of the operand (register or memory ) are

M subtracted from the contents of the accumulator, and the

result is stored in the accumulator. If the operand is a

memory location, its location is specified by the contents of

the HL registers. All flags are modified to reflect the result of

the subtraction.

Example: SUB B or SUB M

Subtract source and borrow from accumulator

SBB R The contents of the operand (register or memory ) and

M the Borrow flag are subtracted from the contents of the

accumulator and the result is placed in the accumulator. If

the operand is a memory location, its location is specified by

the contents of the HL registers. All flags are modified to

reflect the result of the subtraction.

Example: SBB B or SBB M

Subtract immediate from accumulator

SUI 8-bit data The 8-bit data (operand) is subtracted from the contents of the

accumulator and the result is stored in the accumulator. All

flags are modified to reflect the result of the subtraction.

Example: SUI 45

Subtract immediate from accumulator with borrow

SBI 8-bit data The 8-bit data (operand) and the Borrow flag are subtracted

from the contents of the accumulator and the result is stored

in the accumulator. All flags are modified to reflect the result

of the subtracion.

Example: SBI 45

Increment register or memory by 1

INR R The contents of the designated register or memory) are

M incremented by 1 and the result is stored in the same place. If

the operand is a memory location, its location is specified by

the contents of the HL registers.

Example: INR B or INR M

Increment register pair by 1

INX R The contents of the designated register pair are incremented

by 1 and the result is stored in the same place.

Example: INX H

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Decrement register or memory by 1

DCR R The contents of the designated register or memory are

M decremented by 1 and the result is stored in the same place. If

the operand is a memory location, its location is specified by

the contents of the HL registers.

Example: DCR B or DCR M

Decrement register pair by 1

DCX R The contents of the designated register pair are decremented

by 1 and the result is stored in the same place.

Example: DCX H

Decimal adjust accumulator

DAA none The contents of the accumulator are changed from a binary

value to two 4-bit binary coded decimal (BCD) digits. This is

the only instruction that uses the auxiliary flag to perform the

binary to BCD conversion, and the conversion procedure is

described below. S, Z, AC, P, CY flags are altered to reflect

the results of the operation.

If the value of the low-order 4-bits in the accumulator is

greater than 9 or if AC flag is set, the instruction adds 6 to the

low-order four bits.

If the value of the high-order 4-bits in the accumulator is

greater than 9 or if the Carry flag is set, the instruction adds 6

to the high-order four bits.

Example: DAA

8085 Instruction Set Page 7

BRANCHING INSTRUCTIONS

Opcode Operand Description

Jump unconditionally

JMP 16-bit address The program sequence is transferred to the memory location

specified by the 16-bit address given in the operand.

Example: JMP 2034 or JMP XYZ

Jump conditionally

Operand: 16-bit address

The program sequence is transferred to the memory location

specified by the 16-bit address given in the operand based on

the specified flag of the PSW as described below.

Example: JZ 2034 or JZ XYZ

Opcode Description Flag Status

JC Jump on Carry CY = 1

JNC Jump on no Carry CY = 0

JP Jump on positive S = 0

JM Jump on minus S = 1

JZ Jump on zero Z = 1

JNZ Jump on no zero Z = 0

JPE Jump on parity even P = 1

JPO Jump on parity odd P = 0

8085 Instruction Set Page 8

Unconditional subroutine call

CALL 16-bit address The program sequence is transferred to the memory location

specified by the 16-bit address given in the operand. Before

the transfer, the address of the next instruction after CALL

(the contents of the program counter) is pushed onto the stack.

Example: CALL 2034 or CALL XYZ

Call conditionally

Operand: 16-bit address

The program sequence is transferred to the memory location

specified by the 16-bit address given in the operand based on

the specified flag of the PSW as described below. Before the

transfer, the address of the next instruction after the call (the

contents of the program counter) is pushed onto the stack.

Example: CZ 2034 or CZ XYZ

Opcode Description Flag Status

CC Call on Carry CY = 1

CNC Call on no Carry CY = 0

CP Call on positive S = 0

CM Call on minus S = 1

CZ Call on zero Z = 1

CNZ Call on no zero Z = 0

CPE Call on parity even P = 1

CPO Call on parity odd P = 0

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Return from subroutine unconditionally

RET none The program sequence is transferred from the subroutine to

the calling program. The two bytes from the top of the stack

are copied into the program counter, and program execution

begins at the new address.

Example: RET

Return from subroutine conditionally

Operand: none

The program sequence is transferred from the subroutine to

the calling program based on the specified flag of the PSW as

described below. The two bytes from the top of the stack are

copied into the program counter, and program execution

begins at the new address.

Example: RZ

Opcode Description Flag Status

RC Return on Carry CY = 1

RNC Return on no Carry CY = 0

RP Return on positive S = 0

RM Return on minus S = 1

RZ Return on zero Z = 1

RNZ Return on no zero Z = 0

RPE Return on parity even P = 1

RPO Return on parity odd P = 0

8085 Instruction Set Page 10

Load program counter with HL contents

PCHL none The contents of registers H and L are copied into the program

counter. The contents of H are placed as the high-order byte

and the contents of L as the low-order byte.

Example: PCHL

Restart

RST 0-7 The RST instruction is equivalent to a 1-byte call instruction

to one of eight memory locations depending upon the number.

The instructions are generally used in conjunction with

interrupts and inserted using external hardware. However

these can be used as software instructions in a program to

transfer program execution to one of the eight locations. The

addresses are:

Instruction Restart Address

RST 0 0000H

RST 1 0008H

RST 2 0010H

RST 3 0018H

RST 4 0020H

RST 5 0028H

RST 6 0030H

RST 7 0038H

The 8085 has four additional interrupts and these interrupts

generate RST instructions internally and thus do not require

any external hardware. These instructions and their Restart

addresses are:

Interrupt Restart Address

TRAP 0024H

RST 5.5 002CH

RST 6.5 0034H

RST 7.5 003CH

8085 Instruction Set Page 11

LOGICAL INSTRUCTIONS

Opcode Operand Description

Compare register or memory with accumulator

CMP R The contents of the operand (register or memory) are

M compared with the contents of the accumulator. Both

contents are preserved . The result of the comparison is

shown by setting the flags of the PSW as follows:

if (A) < (reg/mem): carry flag is set, s=1

if (A) = (reg/mem): zero flag is set, s=0

if (A) > (reg/mem): carry and zero flags are reset, s=0

Example: CMP B or CMP M

Compare immediate with accumulator

CPI 8-bit data The second byte (8-bit data) is compared with the contents of

the accumulator. The values being compared remain

unchanged. The result of the comparison is shown by setting

the flags of the PSW as follows:

if (A) < data: carry flag is set, s=1

if (A) = data: zero flag is set, s=0

if (A) > data: carry and zero flags are reset, s=0

Example: CPI 89

Logical AND register or memory with accumulator

ANA R The contents of the accumulator are logically ANDed with

M the contents of the operand (register or memory), and the

result is placed in the accumulator. If the operand is a

memory location, its address is specified by the contents of

HL registers. S, Z, P are modified to reflect the result of the

operation. CY is reset. AC is set.

Example: ANA B or ANA M

Logical AND immediate with accumulator

ANI 8-bit data The contents of the accumulator are logically ANDed with the

8-bit data (operand) and the result is placed in the

accumulator. S, Z, P are modified to reflect the result of the

operation. CY is reset. AC is set.

Example: ANI 86

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Exclusive OR register or memory with accumulator

XRA R The contents of the accumulator are Exclusive ORed with

M the contents of the operand (register or memory), and the

result is placed in the accumulator. If the operand is a

memory location, its address is specified by the contents of

HL registers. S, Z, P are modified to reflect the result of the

operation. CY and AC are reset.

Example: XRA B or XRA M

Exclusive OR immediate with accumulator

XRI 8-bit data The contents of the accumulator are Exclusive ORed with the

8-bit data (operand) and the result is placed in the

accumulator. S, Z, P are modified to reflect the result of the

operation. CY and AC are reset.

Example: XRI 86

Logical OR register or memory with accumulaotr

ORA R The contents of the accumulator are logically ORed with

M the contents of the operand (register or memory), and the

result is placed in the accumulator. If the operand is a

memory location, its address is specified by the contents of

HL registers. S, Z, P are modified to reflect the result of the

operation. CY and AC are reset.

Example: ORA B or ORA M

Logical OR immediate with accumulator

ORI 8-bit data The contents of the accumulator are logically ORed with the

8-bit data (operand) and the result is placed in the

accumulator. S, Z, P are modified to reflect the result of the

operation. CY and AC are reset.

Example: ORI 86

Rotate accumulator left

RLC none Each 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. S, Z, P,

AC are not affected.

Example: RLC

Rotate accumulator right

RRC none Each 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. S, Z, P,

AC are not affected.

Example: RRC

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Rotate accumulator left through carry

RAL none Each 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. S, Z, P, AC

are not affected.

Example: RAL

Rotate accumulator right through carry

RAR none Each binary bit of the accumulator is rotated right by one

position through the Carry flag. Bit D0 is placed in the Carry

flag, and the Carry flag is placed in the most significant

position D7. CY is modified according to bit D0. S, Z, P, AC

are not affected.

Example: RAR

Complement accumulator

CMA none The contents of the accumulator are complemented. No flags

are affected.

Example: CMA

Complement carry

CMC none The Carry flag is complemented. No other flags are affected.

Example: CMC

Set Carry

STC none The Carry flag is set to 1. No other flags are affected.

Example: STC

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CONTROL INSTRUCTIONS

Opcode Operand Description

No operation

NOP none No operation is performed. The instruction is fetched and

decoded. However no operation is executed.

Example: NOP

Halt and enter wait state

HLT none The 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

Disable interrupts

DI none The interrupt enable flip-flop is reset and all the interrupts

except the TRAP are disabled. No flags are affected.

Example: DI

Enable interrupts

EI none The interrupt enable flip-flop is set and all interrupts are

enabled. No flags are affected. After a system reset or the

acknowledgement of an interrupt, the interrupt enable flip-

flop is reset, thus disabling the interrupts. This instruction is

necessary to reenable the interrupts (except TRAP).

Example: EI

8085 Instruction Set Page 15

Read interrupt mask

RIM none This 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

Set interrupt mask

SIM none This 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: SIM