8085 microprocessor :: Instruction naming conventions:

Instruction Naming Conventions:


The mnemonics assigned to the instructions are designed to indicate the function of the instruction. The instructions fall into the following functional categories:


Data Transfer Group:

The data transfer instructions move data between registers or between memory and registers.


MOV           Move

MVI           Move Immediate

LDA           Load Accumulator Directly from Memory

STA           Store Accumulator Directly in Memory

LHLD          Load H & L Registers Directly from Memory

SHLD          Store H & L Registers Directly in Memory


An 'X' in the name of a data transfer instruction implies that it deals with a register pair (16-bits);

LXI           Load Register Pair with Immediate data

LDAX          Load Accumulator from Address in Register Pair

STAX          Store Accumulator in Address in Register Pair

XCHG          Exchange H & L with D & E

XTHL          Exchange Top of Stack with H & L

Arithmetic Group:

The arithmetic instructions add, subtract, increment, or decrement data in registers or memory.

ADD           Add to Accumulator

ADI           Add Immediate Data to Accumulator

ADC           Add to Accumulator Using Carry Flag

ACI           Add Immediate data to Accumulator Using Carry

SUB           Subtract from Accumulator

SUI           Subtract Immediate Data from Accumulator

SBB           Subtract from Accumulator Using Borrow (Carry) Flag

SBI           Subtract Immediate from Accumulator Using Borrow (Carry) Flag

INR           Increment Specified Byte by One

DCR           Decrement Specified Byte by One

INX           Increment Register Pair by One

DCX           Decrement Register Pair by One

DAD           Double Register Add; Add Content of Register

              Pair to H & L Register Pair

Logical Group:

This group performs logical (Boolean) operations on data in registers and memory and on condition flags.

The logical AND, OR, and Exclusive OR 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

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

Branch Group:

The branching instructions alter normal sequential program flow, either unconditionally or conditionally. The unconditional branching instructions are as follows:

JMP           Jump

CALL          Call

RET           Return

Conditional branching instructions examine the status of one of four condition flags to determine whether the specified branch is to be executed. The conditions that may be specified are as follows:

NZ            Not Zero (Z = 0)

Z             Zero (Z = 1)

NC            No Carry (C = 0)

C             Carry (C = 1)

PO            Parity Odd (P = 0)

PE            Parity Even (P        = 1)

P             Plus (S = 0)

M             Minus (S = 1)

Thus, the conditional branching instructions are specified as follows:

Jumps         Calls        Returns

C             CC            RC      (Carry)

INC           CNC           RNC     (No Carry)

JZ            CZ            RZ      (Zero)

JNZ           CNZ           RNZ     (Not Zero)

JP            CP            RP      (Plus)

JM            CM            RM      (Minus)

JPE           CPE           RPE     (Parity Even)

JP0           CPO           RPO     (Parity Odd)

Two other instructions can affect a branch by replacing the contents or the program counter:

PCHL          Move H & L to Program Counter

RST           Special Restart Instruction Used

              with Interrupts






anonymous   said:
6 years ago

Give some examples for logic rotate branch group

Points :   0




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