How does the 68000 internally represent instructions?

Question

How does the 68000 internally represent instructions. I've read that there are different types of instructions: single effective operation word format instructions, brief and full extension word format instructions. The single effective operation word instruction seems to represent the instruction and the lower 6 bits of this instruction the addressing mode and register. Does this addressing mode and register tell you if there follows a brief or full extension word format instruction, which on his turn represents the operands for the instruction. Do you know a better manual than the 68000 programming reference manual.

Thanks in advance

Answer 1

The actual internal representation is a combination of "microcode" and "nanocode". The 68000 has 544 17-bit microcode words which dispaches to 366 68-bit nanocode words.

While this may not be what you wanted to know, this link may provide some insights:

http://www.easy68k.com/paulrsm/doc/dpbm68k1.htm