A micro program control unit is required to generate a total...

A micro program control unit is required to generate a total of 30 control signals. Assume that during any micro instruction, almost two control signals are active. Minimum number of bits required in the control word to generate the required control signals will be (A) 2 (B) $2.5$ (C) 10 (D) 12

Key Concepts

Microprogrammed Control Unit

A microprogrammed control unit uses microinstructions that are stored in a control memory to generate the sequence of control signals required for executing higher-level instructions. It decomposes complex operations into simpler micro-operations, leveraging a controlled and predictable set of signals to effectively orchestrate the CPU's functionality.

Control Signals

Control signals are binary indicators used to manage and synchronize the functioning of various components within a computer system. Their activation directs operations such as data transfer, arithmetic computations, or memory access, playing a crucial role in the execution of instructions.

Encoding of Control Words

Instead of assigning one bit per control signal (which would require 30 bits in a one-hot encoding scheme), the control word can be encoded by specifying indices of the active signals. Since only a few (in this case, about two) signals are active at any one time, using binary encoding to represent these indices minimizes the number of bits needed in the microinstruction.

Binary Encoding Requirements

To uniquely encode one control signal out of 30, approximately ?log?(30)? bits (about 5 bits) are required. If two signals are to be selected concurrently, encoding each with 5 bits results in a total of 10 bits. This approach thus reduces the overall control word width compared to a full one-hot encoding, making it an efficient solution.

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