Instruction Set 8085

Example: NOP

Example: HLT

The interrupt enable flip-flop is reset and all the interrupts except the TRAP are disabled. No flags are affected.

Example: DI

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 flipflop is reset, thus disabling the interrupts. This instruction is
necessary to reenable the interrupts (except TRAP).

Example: EI


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

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

R

M

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
if (A) = (reg/mem): zero flag is set
if (A) > (reg/mem): carry and zero flags are reset

Example: CMP B or CMP M

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
if (A) = data: zero flag is set
if (A) > data: carry and zero flags are reset

Example: CPI 89H

R

M

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

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 86H

R

M

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

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 86H

R

M

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

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 86H

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

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

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

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

The contents of the accumulator are complemented. No flags are affected.

Example: CMA

The Carry flag is complemented. No other flags are affected.

Example: CMC

Set Carry

Example: STC

The program sequence is transferred to the memory location specified by the 16-bit address given in the operand.

Example: JMP 2034H or JMP XYZ

 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 2034H or JZ XYZ

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 2034H or CALL XYZ

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

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

 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

 RST

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:

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:

 R

M

The contents of the operand (register or memory) 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: ADD B or ADD M

 R

M

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

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 45H

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 45H

The instruction loads 16-bit data in the register pair designated in the operand.

Example: LXI H, 2034H or LXI H, XYZ

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

 R

M

The contents of the operand (register or memory ) are 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

 R

M

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

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 45H

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

 R

M

The contents of the designated register or memory) are 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

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

Example: INX H

 R

M

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

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

Example: DCX H

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

 Rd, Rs

M, Rs

Rd, M

 This instruction copies the contents of the source register into the destination register; the contents of 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

 Rd, data

M, data

The 8-bit data is stored in the destination register or memory. If the operand is a memory location, its location is specified by the contents of the HL registers.

Example: MVI B, 57H or MVI M, 57H

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 2034H

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

The instruction loads 16-bit data in the register pair designated in the operand.

Example: LXI H, 2034H or LXI H, XYZ

 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 2040H

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 4350H

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

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 2470H

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

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

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

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 highorder 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

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

 The contents of the accumulator are copied into the I/O port specified by the operand.

Example: OUT F8H

The contents of the input port designated in the operand are read and loaded into the accumulator.

Example: IN 8CH