Micro-programmed control control unit

An alternative way to implement control unit is micro programmed control unit in which the logic of the
control unit is specified by micro program.A micro-program consists of sequence of micro instruction in a micro programming language.On executing these micro instruction, they are responsible for:-

1. Execute one or more micro operation 

2. Sequencing through micro operation i.e information about micro instruction that to be executed           next.

The micro program is also known as firmware.Firmware is a mid way between hardware and software.Firmware in comparison to hardware is easier to design whereas in comparison to software, it si difficult to write and design.

               A control unit provides a set of control signal distributed throughout the CPU with each of the lone representing binary digits '0' or '1' therefore micro instruction is made responsible for generating control signal for desired control lines to implement desired micro-operation.

            So,each micro-instruction can generate a set of control signals on control lines.A set of control signals control with which bit representing a single control line is called control word.