Logical instruction of 8085

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Logical Instruction Of 8085Logical Instruction Of 8085

Instruction Set of 8085
An instruction is a binary pattern designed inside a
microprocessor to perform a specific function.
The entire group of instructions that a microprocessor
supports is called Instruction Set.
8085 has 246 instructions.
Each instruction is represented by an 8-bit binary value.
These 8-bits of binary value is called Op-Code or
Instruction Byte.

Classification of Instruction Set
Data Transfer Instruction
Arithmetic Instructions
Branching Instructions
Control Instructions
Logical Instructions

Logical Instructions
These instructions perform logical operations on data
stored in registers, memory and status flags.
The logical operations are:
AND
OR
XOR
Rotate
Compare
Complement

AND, OR, XOR
Any 8-bit data, or the contents of register, or memory
location can logically have
AND operation
OR operation
XOR operation
with the contents of accumulator.
The result is stored in accumulator.

Rotate
Each bit in the accumulator can be shifted either left
or right to the next position.

Compare
Any 8-bit data, or the contents of register, or memory
location can be compares for:
Equality
Greater Than
Less Than
with the contents of accumulator.
The result is reflected in status flags.

Complement
The contents of accumulator can be complemented.
Each 0 is replaced by 1 and each 1 is replaced by 0.

Opcode Operand Description
CMP R
M
Compare register or memory with
accumulator
The contents of the operand (register or memory) are
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:

CMP R
M
Compare register or memory with
accumulator
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 8-bit data is compared with the contents of
accumulator.
The values being compared remain unchanged.
The result of the comparison is shown by setting the
flags of the PSW as follows:

CPI 8-bit data Compare immediate with accumulator
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 the
contents of register or memory.
The result is placed in the accumulator.
If the operand is a memory location, its address is specified by the
contents of H-L pair.
S, Z, P are modified to reflect the result of the operation.
CY is reset and 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.
S, Z, P are modified to reflect the result.
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 XORed with the contents of the register or
memory.
 The result is placed in the accumulator.
 If the operand is a memory location, its address is specified by the contents of H-L pair.
 S, Z, P are modified to reflect the result of the operation.
 CY and AC are reset.
 Example: XRA B or XRA M.

ORA R
M
Logical OR register or memory with
accumulator
 The contents of the accumulator are logically ORed with the contents of the register or
memory.
 The result is placed in the accumulator.
 If the operand is a memory location, its address is specified by the contents of H-L pair.
 S, Z, P are modified to reflect the result.
 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.
CY and AC are reset.
Example: ORI 86H.

XRA R
M
Logical XOR register or memory with
accumulator
The contents of the accumulator are XORed with the contents
of the register or memory.
If the operand is a memory location, its address is specified by
the contents of H-L pair.
S, Z, P are modified to reflect the result of the operation.
Example: XRA B or XRA M.

XRI 8-bit data XOR immediate with accumulator
The contents of the accumulator are XORed with the
8-bit data.
Example: XRI 86H.

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.
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.
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
The Carry flag is set to 1.
No other flags are affected.
Example: STC.

8085 Instruction Set
26
Summary Logical Group
This group performs logical (Boolean) operations on data in
registers and memory and on condition flags.
 These instructions enable you to set specific bits in the
accumulator ON or OFF.
ANA Logical AND with Accumulator
ANI Logical AND with Accumulator Using Immediate
Data
ORA Logical OR with Accumulator
OR Logical OR with Accumulator Using Immediate
Data
XRA Exclusive Logical OR with Accumulator
XRI Exclusive OR Using Immediate Data

8085 Instruction Set
27
The Compare instructions compare the content of an 8-bit value with
the contents of the accumulator;
CMP Compare
CPI Compare Using Immediate Data
The rotate instructions shift the contents of the accumulator one bit
position to the left or right:
RLC Rotate Accumulator Left
RRC Rotate Accumulator Right
RAL Rotate Left Through Carry
RAR Rotate Right Through Carry
Complement and carry flag instructions:
CMA Complement Accumulator
CMC Complement Carry Flag
STC Set Carry Flag

Reference
Microprocessor Architecture, programming, and
Application with the 8085 – Ramesh Gaonkar

Logical instruction of 8085

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