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Instruction Naming Conversions

Microprocessor Tutorials (8085/8085A)

8085 / 8085A
Instruction Naming Conversions

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

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