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Opcodes and Addressing Modes

This MCU uses 8-bit opcodes. A complete instruction consists of a prebyte, if any, an opcode, and zero, one, two, or three operands. Complete instructions can therefore be from one to five bytes long.

Six addressing modes can be used to access memory. They are : immediate, direct, extended, indexed, inherent, and relative. All modes except inherent mode use an effective address. The effective address is the memory address from which the argument is fetched or stored, or the address from which execution is to proceed. The effective address can be specified within an instruction, or it can be calculated. The detailed instruction set is available in the Technical Data Book for MC68HC11E9.



Matanya Elchanani
Wed Dec 18 17:00:21 EST 1996