23. Simplified Multibyte Instructions Cont. (not x86!)

To encode immediate constant values and address modes such as

  0xxxxh          ; immediate mode
  [ 0xxxxh ]      ; direct mode
  [ 0xxxxh + bx ] ; fixed base + reg

we add two bytes of 16-bit address or constant value to the opcode:

• low-order byte immediately follows the opcode byte in memory, and

• high-order byte comes after that.

Simplified multibyte instruction encoding:

Three-byte encoding for MOV AX, [1000h] instruction becomes

    C6 00 10

and the three-byte encoding for MOV AX, [2000h] is

    C6 00 20