LOGICAL OPERATIONS IN 8085 MICROPROCESSOR

B.RAMA PRABHA
ASSISTANT PROFESSOR,
DEPARTMENT OF COMPUTER SCIENCE,
K.C.S.KASI NADAR COLLEGE OF ARTS & SCIENCE,
CHENNAI-21

LOGICAL OPERATIONS
A Microprocessor is a programmable logic chip.it
can perform all logic functions of the hard wired
logic through its instruction set.The 8085 instruction
set includes such logic function such as
AND,OR,EX-OR,COMPLEMENT.
2

LOGICAL OPERATIONS
The opcode of the logical functions are as follows.
 AND – AND (Logical AND with a content of Register)
 ANI – AND IMMEDIATE (Logical AND 8-bit data)
 ORA – OR (Logical OR with a content of Register)
 ORI – OR IMMEDIATE(Logical OR 8-bit data)
 XRA – X-OR(Logical X-OR with a content of Register)
 XRI – X-OR IMMEDIATE(Logical X-OR 8-bit data)
3

AND Logic Instructions
ANA(LOGICAL AND)
 This is a one byte instruction
 The contents of a register or any memory location are logically
ANDed with the contents stored in the accumulator register. The
resulting answer is saved in the accumulator.
Example : ANA B , ANA 2000H
4
The Opcode The Operands Description
ANA
R Logical AND the register with accumulator
M
Logical AND the contents pointed by the memory
address pointed by the HL pair (M) with the contents
of the accumulator

ANI (AND IMMEDIATE)
 This is a two byte instruction
 The ANI instruction works exactly like the ANA instruction but
performs logical AND of 8-bit immediate value with the contents of
the accumulator register..
Example : ANI 04H 5
ANI 8-bit immediate data Logically AND immediate data with accumulator

OR Logic Instructions
ORA(LOGICAL OR)
ORed with the contents stored in the accumulator register. The
resulting answer is saved in the accumulator.
Example : ORA B ,ORA 7580H
6
ORA
R Logical OR the register with accumulator
M
Logical OR the contents of the memory location
pointed by the HL pair (M) with the contents of the
accumulator

OR Logic Instructions
ORI(LOGICAL OR WITH DATA)
 The ORI instruction works exactly like the ORA instruction but
performs logical OR of 8-bit immediate value with the contents of
the accumulator register.
Example : ORI 44H 7
ORI 8-bit immediate data Logically OR immediate data with accumulator

XRA (LOGICALLY OR WITH REGISTER OR MEMORY LOCATION)
XORed with the contents stored in the accumulator register. The
resulting answer is saved in the accumulator. If the operand
happens to be a memory location, then its address is mentioned by
the contents of the H-L pair.
Example : XRA B ,XRA 7580H
8
XRA
R Logical XOR the register with accumulator
M
Logical XOR the contents of the memory address
pointed by the HL pair (M) with the contents of the
accumulator

XRI(LOGICALLY OR WITH DATA)
 The XRI instruction works exactly like the XRA instruction but
performs logical XOR of 8-bit immediate value with the contents of
the accumulator register
Example : XRI 44H
9
XRI 8-bit immediate data Logically XOR immediate data with accumulator

Rotate Instructions
RLC(ROTATE ACCUMULATOR LEFT)
 This is a ONE byte instruction
 The RLC instruction causes each binary bit in the accumulator register to be rotated by one
position to its left. The MSB value is shifted to the LSB as well as the Carry Flag in the
PSW. The other PSW bits, such as S, Z, P, or AC, are not affected by this
operation.Example : RLC
10
RLC None Rotate Accumulator Left

Rotate Instructions
RRC(ROTATE ACCUMULATOR RIGHT)
 The RRC instruction causes each binary bit in the accumulator register to be rotated by one
position to its right. The LSB value is shifted to the MSB as well as the Carry Flag in the
PSW. The other PSW bits, such as S, Z, P, or AC, are not affected by this
operation.Example : RRC
11
RRC None Rotate Accumulator Right

Rotate Instructions
RAL(ROTATE ACCUMULATOR LEFT WITH CARRY)
 The RAL instruction causes each binary bit in the accumulator register to be rotated by one
position to its left through the carry flag as well. The MSB value is shifted to the Carry
Flag, and the Carry Flag in the PSW is shifted to the LSB.Example : RAL
12
RAL None Rotate Accumulator Left including the Carry

Rotate Instructions
RAL(ROTATE ACCUMULATOR LEFT)
 The RAL instruction causes each binary bit in the accumulator register to be rotated by one
position to its left through the carry flag as well. The MSB value is shifted to the Carry
Flag, and the Carry Flag in the PSW is shifted to the LSB.Example : RAL
13
RAL None Rotate Accumulator Left including the Carry

Complement Instructions
CMA(COMPLEMENT ACCUMULATOR)
 The CMA instruction complements the Content of the accumulator. No flags are affected.
 Example : CMA
14
CMA None Complement Accumulator

Complement Instructions
CMC(COMPLEMENT CARRY FLAG)
 The CMC instruction complements the Carry Flag bit. The other PSW bits, such as S, Z, P,
or AC, are not affected by this operation.
Example : CMC
15
CMC None Complement Carry Flag

Set Instruction
STC(SET CARRY FLAG)
 The STC instruction sets the Carry Flag bit to 1. The other PSW bits, such as S, Z, P, or
AC, are not affected by this operation
Example : STC
16
STC None Set Carry Flag

LOGICAL OPERATIONS IN 8085 MICROPROCESSOR

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