Keil Software — A51/AX51/A251 Macro Assembler and Utilities |
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instructions in your program into machine code and stores the resulting code in an object file.
Assembly instructions have the following general format:
label: mnemonic operand , operand , operand ; comment |
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where |
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label |
is a symbol name that is assigned the address at which the |
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instruction is located. |
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mnemonic |
is the ASCII text string that symbolically represents a |
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machine language instruction. |
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operand |
is an argument that is required by the specified mnemonic. |
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comment |
is an optional description or explanation of the instruction. |
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A comment may contain any text you wish. Comments are |
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ignored by the assembler. |
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The “Instruction Sets” of the x51 microcontrollers are listed on page 40 by mnemonic and by machine language opcode. Refer to this section for more information about assembler instructions.
Comments
Comments are lines of text that you may include in your program to identify and explain the program. Comments are ignored by the Ax51 assembler and are not required in order to generate working programs.
You can include comments anywhere in your assembler program. Comments must be preceded with a semicolon character (;). A comment can appear on a line by itself or can appear at the end of an instruction. For example:
;This is a comment
NOP |
;This is also a comment |
When the assembler recognizes the semicolon character on a line, it ignores subsequent text on that line. Anything that appears on a line to the right of a semicolon will be ignored by the Ax51 assembler. Comments have no impact on object file generation or the code contained therein.
Shaded directives and options are available only in AX51 and A251.