ASSEMBLER DIRECTIVES

✏️ASSEMBLER DIRECTIVES

Assembler directives are instructions that direct the assembler to do something. This is used to set the program or register address during assembly.

✏️Types of assembler directives are:

📌ORG (origin):-

 The origin (ORG) directive is used to indicate the beginning of the addresses the number that comes after ORG can be either in hex or in decimal if the number is not followed by H it is decimal and the assembler will convert it to hex.

         Ex:- ORG 0000H

📌EQU (equate):-

    This is used to define a constant without occupying a memory location. The EQU directive does not set aside storage for a data item but associates a constant value with a data label so that when the label appears in the program its constant value will be substituted for the label to use EQU for the counter constant and then the constant is used to load the register.

   Ex:-

       COUNT EQU 25

       MOV R3, # COUNT

📌END:-

The END directive indicates to the assembler at the end of the source (asm) file.The END directive is the last line of an 8051 program meaning that in the source code anything after the END directive is ignored by the assembler.

📌DB (define byte) :-

The define assembler directive is used for allocation of storage space. It can be used to reserve as well as initialize one or more bytes.

📌DW (define word) :-

Define Word [DW]- The DW directive defines items that are one word (two bytes) in length.

Define Double word [DD]- It defines the data items that are a double word (four bytes) in length.

Define Quad word [DQ]- This directive is used to tell the assembler to declare variable 4 words in length or to reserve 4 words of storage in memory.