After using this directive, every appearance of the label ³MAXIMUM´ in the program will be interpreted by the assembler as the number 99 (MAXIMUM = 99). The Appendix includes information on the and MCS instruction set, a summary of directives and controls, the differences between assembler versions. ASSUME Directive. -. The ASSUME directive is used to tell the assembler that the name of the logical segment should be used for a specified segment.

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Can directivss useful for strings, which contain a single quote such as “O’Really”. Foremost among the reserved words are the mnemonics for the instructions. The job of the programmer is to break down data larger than 8 bits [00 to FFH, or 0 to in decimal] to be processed by the CPU.

Following are some DB examples: Another important pseudocode is the END directive. EQU is used to define a constant without occupying a memory location. The ORG directive is used to indicate the beginning of the address. Some assembler uses “. If the number is not followed by ‘H’, it is decimal and the assembler will convert it into hex.

This is used to define a constant without occupying a memory location. Check your assembler for the list of reserved words.


In this section we look at some widely used data types and directives supported by the assembler. Facebook Like For Iamtechnical.


Every assembler has some reserved words that must not be used assembbler labels in the program. For decimal, the “D” after the decimal number is optional, but using “B” [binary] and “H” [hexadecimal] is required.

Explain assembler directives.

It is used to define the 8-bit data. First, each label name must be unique. The answer is that, lets say in a program there asssmbler a constant value [a fixed value] used in many different places in the program, and the programmer wants to change its value through out the entire program.

DB is also used to allocate memory in byte-sized chunks. By choosing label names that are meaningful, a programmer can make a program much easier to read and maintain. The following are some more widely used directives of the These reserve words are the mnemonics for the instructions e. This indicates to the assembler the end of the source asm file.


There are several rules that names must follow. In other words it cannot be a number. The names used for labels in Assembly language programming consist of alphabetic letters in both uppercase and lowercase, the digits 0 through 9, and the special characters question mark?

Like us on Facebook. The first character of the label must be an alphabetic character. What is the advantage of eirectives EQU?


The data type used by the can be positive or negative. END indicates to the assemblere the end of the source [asm ] file. In assembly language programming anything after the END directive is ignored by the assembler. The microcontroller has only one data type. Programmer can make a program easier directkves read and maintain by choosing label names that are meaningful.


If the number is not followed by H, it is decimal and the assembler will convert it to hex. A discussion of signed numbers is given in Chapter 6.

It is 8 bits, and the size of each register is also 8 bits. By the use of EQU, a programmer can change all valves at once and the assembler will change all of it occurrences, rather than search the entire program and to change the value one by one to fine every occurrence, just change the constant value followed by EQU results changing the all occurrences at once.

Assume that there is a constant a fixed value used in many different places in the program, and the programmer wants to change its value throughout. The END directive is the last line of an program. Labels in Assembly Language Programming and its Rules: For examples of how to process data larger than 8 bits, see Chapter 6.

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The assembler will convert the numbers in hex. The DB directive is the most widely used data directive in the assembler.