8085 is details

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 1

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


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


ARITHMETIC INSTRUCTIONS


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
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


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
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 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


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 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


BRANCHING INSTRUCTIONS


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


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

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


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

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


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


LOGICAL INSTRUCTIONS


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


Exclusive OR register or memory with accumulator
XRA R The contents of the accumulator are Exclusive ORed with
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
Example: XRI 86

Logical OR register or memory with accumulaotr
ORA R The contents of the accumulator are logically ORed with
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
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


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


CONTROL INSTRUCTIONS


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


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


8085 is details

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