Using the Section Directive · Setting up the Linker · Running the Assembler from the Command Line MICROPROCESSOR INSTRUCTION REFERENCE ACI. The most commonly used assembler directives are ORG, DB, DW, EQU, and END. For example, 0 ORG C 1 00H directive informs the assembler to assemble. Assembly Language Format Assembler Example Description. Directive. ORG ( Origin) ORG H The *Please Refer to Assembly Code Summary.
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This shortens the source code. DT — Define Ten Bytes.
Assembler User Guide
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. DW — Define Word. DB — Define Byte This directive is used to declare a byte type variable or to store a byte in memory location. Executable statements- These are the statements to be executed by the processor.
8085 Assembler User Guide
MODEL- This directive is used for selecting a standard memory model for the assembly language program. The assembler directives can be divided into two categories namely the general purpose directives and the special directives. If the word is at even address can read a memory in 1 bus cycle. This directive is used with name of the segment to indicate the end of that logic segment.
ALIGN- This directive will tell the assembler to align the next instruction on an address which corresponds to the given value.
INCLUDE- This directive is used to tell the assembler to insert a block of source code from the named file into the current source module. 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 Directivess label directives Scope directives Listing control directives Miscellaneous directives. Each memory model has various limitations depending on microprcessor maximum space if for code and data.
A series of words can be read much more quickly if they are at even address. CODE [name] The name in this format is optional. Mohaimen Himu October 24, at CODE- This assembler directive indicates the beginning of the code segment. Assembly language consists of two types of statements viz. Write short notes on assembler directives. DB — Define Byte. END- This is placed at the end of a source and it acts as directiges last statement of a program.
As the name says, it directs the assembler to do a task. This directive is used to declare a byte type variable or to store a byte in memory location.
This is because the END directive terminates the entire program. Engineering in your pocket Download our mobile app and study on-the-go. You get question papers, syllabus, subject analysis, answers – all in one app. This directive is used to group the logical segments named after the directive into one logical group segment. This directive is used to define a variable which is 10 mucroprocessor in length or to reserve 10 bytes of storage in the memory. Define Double word [DD]- It defines the data items that are a double word four bytes in length.
This directive is used to give a name to some value or to a symbol. DD — Define Doubleword.
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. DQ — Define Quadword. If the word starts at an odd address, the will take 2 bus cycles to get the data.