This is an encoding of the microinstruction, the microinstruction control i.e., how to refer to the microinstruction control field is encoded to form a control signal.
The micro-coded field directly command field divided into several small fields, the exclusive command microspheres combined in the same field, the compatibility of the different combinations of the micro-command field, each field is coded independently, each command encoding represents a micro defined meanings and each field is coded independently.
The reason is to summarize the knowledge on this issue, I see two different answers, and their biased in favor of one argument.
Example 1:
Example 2:
Analysis: own complete analysis of logical answer Example 2 do not agree with, because at the same time start the three micro-operations, explained in a different field, logical thinking of Example 1 or the use, so there should be three sections, so each piece is 4, may represent up to 16 kinds of operation (the operation can be considered a null operation), the three fields should be a total of 48 modes of operation.
Summary: I still feel that they think is right!