-
Some bits are needed to identify:
-
instruction group
-
instruction code
-
operand types: registers, memory locations, constants.
-
-
All of the above has a direct impact on the instruction size.
-
For example, 8-bit opcode could be split into
-
one 3-bit iii field to describe instruction and its group, and
-
two fields, rr and mmm, (5 bits together) to specify where the instruction operands could be found.
-
-
An opcode byte:
