Detailed description of 8085-Instruction Set

DATA TRANSFER INSTRUCTIONS

Opcode	Operand	Explanation of Instruction	Description
MOV	Rd, Rs M, Rs Rd, M	Copy from source(Rs) to destination(Rd)	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
MVI	Rd, data M, data	Move immediate 8-bit	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
LDA	16-bit address	Load accumulator	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
LDAX	B/D Reg. pair	Load accumulator indirect	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
LXI	Reg. pair, 16-bit data	Load register pair immediate	The instruction loads 16-bit data in the register pair designated in the operand. Example: LXI H, 2034H or LXI H, XYZ
LHLD	16-bit address	Load H and L registers direct	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
STA	16-bit address	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 4350H
STAX	Reg. pair	Store accumulator indirect	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
SHLD	16-bit address	Store H and L registers direct	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
XCHG	none	Exchange H and L with D and E	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
SPHL	none	Copy H and L registers to the stack pointer	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
XTHL	none	Exchange H and L with top of stack	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
PUSH	Reg. pair	Push register pair onto stack	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
POP	Reg. pair	Pop off stack to register 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
OUT	8-bit port address	Output data from accumulator to a port with 8-bit address	The contents of the accumulator are copied into the I/O port specified by the operand. Example: OUT F8H
IN	8-bit port address	Input data to accumulator from a port with 8-bit address	The contents of the input port designated in the operand are read and loaded into the accumulator. Example: IN 8CH

Other Instructions:

ARITHMETIC INSTRUCTIONS

Opcode	Operand	Explanation of Instruction	Description
ADD	R M	Add register or memory, to accumulator	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
ADC	R M	Add register to accumulator with carry	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
ADI	8-bit data	Add immediate to accumulator	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
ACI	8-bit data	Add immediate to accumulator with carry	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
LXI	Reg. pair, 16-bit data	Load register pair immediate	The instruction loads 16-bit data in the register pair designated in the operand. Example: LXI H, 2034H or LXI H, XYZ
DAD	Reg. pair	Add register pair to H and L registers	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
SUB	R M	Subtract register or memory from accumulator	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
SBB	R M	Subtract source and borrow from accumulator	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
SUI	8-bit data	Subtract immediate from accumulator	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
SBI	8-bit data	Subtract immediate from accumulator with borrow	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
INR	R M	Increment register or memory by 1	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
INX	R	Increment register pair by 1	The contents of the designated register pair are incremented by 1 and the result is stored in the same place. Example: INX H
DCR	R M	Decrement register or memory by 1	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
DCX	R	Decrement register pair by 1	The contents of the designated register pair are decremented by 1 and the result is stored in the same place. Example: DCX H
DAA	none	Decimal adjust accumulator	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

Other Instructions:

BRANCHING INSTRUCTIONS

Opcode	Operand	Explanation of Instruction	Description
JMP	16-bit address	Jump unconditionally	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
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	16-bit address	Jump conditionally	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
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	16-bit address	Unconditional subroutine call	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
RET	none	Return from subroutine unconditionally	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
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	none	Return from subroutine conditionally	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
PCHL	none	Load program counter with HL contents	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	0-7	Restart	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 RST1 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

LOGICAL INSTRUCTIONS

Opcode	Operand	Explanation of Instruction	Description
CMP	R M	Compare register or memory with accumulator	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
CPI	8-bit data	Compare immediate with accumulator	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
ANA	R M	Logical AND register or memory with accumulator	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
ANI	8-bit data	Logical AND immediate with accumulator	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
XRA	R M	Exclusive OR register or memory with accumulator	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
XRI	8-bit data	Exclusive OR immediate with accumulator	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
ORA	R M	Logical OR register or memory with accumulator	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
ORI	8-bit data	Logical OR immediate with accumulator	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
RLC	none	Rotate accumulator left	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
RRC	none	Rotate accumulator right	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
RAL	none	Rotate accumulator left through carry	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
RAR	none	Rotate accumulator right through carry	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
CMA	none	Complement accumulator	The contents of the accumulator are complemented. No flags are affected. Example: CMA
CMC	none	Complement carry	The Carry flag is complemented. No other flags are affected. Example: CMC
STC	none	Set Carry	Set Carry Example: STC

 CONTROL INSTRUCTIONS

Opcode	Operand	Explanation of Instruction	Description
NOP	none	No operation	No operation is performed. The instruction is fetched and decoded. However no operation is executed. Example: NOP
HLT	none	Halt and enter wait state	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
DI	none	Disable interrupts	The interrupt enable flip-flop is reset and all the interrupts except the TRAP are disabled. No flags are affected. Example: DI
EI	none	Enable interrupts	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
RIM	none	Read interrupt mas	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
SIM	none	Set interrupt mask	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