Important Assembler Directives of the Microprocessor Data declaration directives: DB, DW, DD, DQ, DT ASSUME END directives EQU. The words defined in this section are directions to the assembler, not instructions for the Richa Upadhyay Prabhu. Microprocessors. Introduction To Segmentation: The microprocessor has 20 bit . The DW directive is used to tell the assembler to define a variable of type.
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There are several other models too. The defined variable may have one or more values in the statement. If there is only one value, four bytes of consecutive memory locations are reserved. The directive DW defines a word -type variable. This is used after the last statement of the program module.
Same is the case with stack and extra segments also, which are only different type aseembler data storage facilities.
This directive informs assembler to reserve one byte of memory space for the variable named WEIGHT and initialize with value The final executable map of the assembly language program is prepared by the loader at the time of loading into the primary memory for actual execution. The program is stored in code segment area. Receive All Updates Via Facebook. Abstract This term paper includes the use of assembler directives in microprocessor and the various assembler directives 886 in Intel microprocessorits format with various examples.
II Use Of Assembler Directives The assembler directives control organization of the program and provide necessary information to the assembler to understand assembly language programs to generate machine codes.
the use of assembler directives in microprocessor
This directive is used together with PROC directive to enclose the procedure. The directive END informs assembler the end of a program module. If there is only one value, 8 bytes of consecutive memory locations are reserved.
This directive informs the assembler to reserve two bytes one word of consecutive memory locations for the variable named SUM and initialize it with the value They generate and store information in the memory. To generate this 20 bit physical address from 2 sixteen bit registers, the following procedure is adopted.
Therefore, the programmer should use END directive at the very end of his program module. This is similar to multiplying four hex numbers by the base The type NEAR is used to call a procedure which is within the program module. The label is used as prefix with directive ENDP. The first phase of assembling is to analyze the program to be converted. So in order to test the program with a different set of data, one need not change the program but only have to alter the data.
Its general format is:. It also analyses the segments used by the program types and labels and their memory requirements. In a given directive statement, there may be single initial value or multiple initial values of the defined variable. An assembler directive is a message to the assembler that tells the assembler something it needs to know in order to carry out the assembly process; for example, an assemble directive tell the assembler where a program is to be located in memory.
The code segment register CS register is to be loaded with the starting address of the code segment, given by the operating system for the label CODE in the assembly language program.
The above directive informs assembler to reserve four bytes of memory locations for the variable named NUMBER and initialize with the number But leave the bytes un-initialized. Microprocesssor there is only one value, 10 bytes of consecutive memory locations are reserved.
An assembler supports directives to define data, to organize segments to control procedures, to define macros etc. It is necessary to do this in any instruction where the micrpprocessor of the operand is not clear.
Assembler Directives & Macros
The general format for ENDP directive is:. The general format microproceszor The second phase looks for the addresses and data assigned to the labels. Type NEAR indicates that the procedure is in the same segment of memory. The general format for ENDP directive is: The directive ENDP informs assembler the end of a procedure.
The low word, H, will be put in memory at a lower address than the high word. The general formula is:. The DS register data segment register is to be loaded with the starting address of the data segment, given by the operating system for the label DATA in the program. The above directive informs the assembler that the name of the data segment is DATA. The instructions are translated to machine codes by the assembler whereas the directives are not translated to micrporocessor codes.
It contains data of the program which is being executed. The above directive informs assembler to reserve 8 bytes of consecutive memory locations for the variable named NUMBER and initialize with the above mentioned number.
the use of assembler directives in microprocessor | CustomWritings
The general format for the EQU directive is:. It is the task of the assembler designer to select the suitable strings for using them as directives,pseudo operands or reserved words and decides syntax. If there are multiple values, ten consecutive memory locations are reserved for each value.
The directive DT assrmbler a variable of ten bytes. This directive informs the assembler to reserve the number of bytes of memory space equal to the number of characters in the string named Microprocezsor, and initialize the memory locations with ASCII codes of the these characters.
When assembler begins assembly process, it initializes a location counter to keep the track of memory locations i. The above directive tells the assembler that the name of the stack segment used by the programmer is STACK.