Definition: An instruction acts on any number of operands.The way an instruction accesses its operands is called its Addressing modes.
Operands may be of three types :
- Both Implicit and Explicit.
Implicit operands mean that the instruction by definition has some specific operands. The programmers do NOT select these operands.
|Example: Implicit operands|
XLAT ; automatically takes AL and BX as operands
|Example: Explicit operands|
MOV AX, BX; it takes AX and BX as operands
Implicit and explicit operands
|Example: Implicit/Explicit operands|
MUL BX; automatically multiply BX explicitly times AX
The location of an operand value in memory space is called the Effective Address (EA)
We can classify the addressing modes of 8086 into four groups:
- Immediate addressing
- Register addressing
- Memory addressing
- I/O port addressing
The first three Addresssing modes are clearly explained.