20. Simplified Instruction Encoding, Cont. (not x86!)

There are three iii encoding groups:

1. Special instruction class iii=000 is reserved for instruction set expansion in the future.

2. Two forms of the MOV instruction include:

   • iii=110 specifies rr field is the destination,

   • iii=111 specifies mmm field is the destination.

3. Remaining codes belong to ADD, SUB, CMP, AND, and OR instructions:

Another opcode field, rr, contains the destination register,

...except for MOV whose iii = 111, in which case rr specifies the source register.

Third bit field, mmm, encodes the source operand (again, except MOV whose iii = 111.)