ASSEMBLER DIRECTIVES OF 80386 PDF

Introduction To Segmentation: The microprocessor has 20 bit address pins; these are capable of addressing 1MegaByte memory. Causes all segments to default to DWORD alignmentP enabled assembly of all instructions (see) enabled assembly of instructions . This directive tells the assembler the name of the logical segment it should use for a specified segment. For example ASSUME CS:CODE, tells.

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MICROPROCESSOR AND MICROCONTROLLER: Assembler Directives of /

Rest will be added with time……. CODE- This assembler directive indicates the beginning of the code segment.

It consists of the entire instruction set of EVEN This directive instructs the assembler to increment the location of the counter to the next even address if it is not already in the even address. The data is stored in data segment area. The EVEN directive updates the location counter to the next even address, if the current location counter contents are not aassembler, and assigns the following routine or variable or constant to that address.

MODEL- This directive is used for selecting a standard memory model for the assembly language program. GROUP This directive virectives used to group the logical segments named after the directive into one logical group segment. The specialty of these statements is that they are effective only during the assembly of a program but they do not generate any code that is machine executable.

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It also idrectives the segments used by the program types and labels and their memory requirements.

As the name says, it directs the assembler to do a task. To generate this 20 bit physical address from 2 sixteen bit registers, the following procedure is adopted. This directive is used to form logical groups of segments with similar purpose or type. When all the modules are working correctly, their object code files are linked together to form the complete program. The program is stored in code segment area.

DB — Define Byte. The PROC directive marks the start of a named procedure in the statement. Like Us On FaceBook! Group the Related Segments: This shortens the source code. If the word is at even address can read a memory in 1 bus cycle.

Macro Assembler Directives

Its format is as follows: This directive indicates the assembler that the label following FAR PTR is not available within the same segment and the address of the bit is of 32 bits i. This directive is used lf declare a byte type variable or to store a byte in memory location.

They are classified into the following categories based on the function performed by them- Simplified segment directives Data allocation directives Segment directives Macros related directives Code label directives Scope directives Listing control directives Miscellaneous directives. The contents of the segment registers are shifted left four times with zeroes 0? If the word starts at an odd address, the will take 2 bus cycles to get the data.

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DD — Define Doubleword This directive is used to define a variable of type doubleword or to reserve storage location of type doubleword in memory.

Write short notes on assembler directives

Additional aszembler are often added to a SEGMENT directive statement to indicate some special way in which we want the assembler to treat the segment.

This directive tells the assembler the name of the logical segment it should use for a specified segment. They generate and store information in the memory.

The DB directive is used to reserve byte or bytes of memory locations in the rirectives memory. The Addressing Modes. Each module is individually assembled, tested, and debugged.

The END directive marks the end of an assembly language program. The assembler prepares the relocation and linkages information subroutine, ISR for fo. But leave the bytes un-initialized.