ABSTRACT
The design of a CPU (central processing unit) essentially consists of two typical individual parts: the control unit and the data processing unit. This chapter explains the need for a control unit that manages the operations of resources, including the CPU operations, at the time of program execution. The design issues of a control unit with the related logic, the different types of control unit signals, and the design of a generic control unit module have been described here with its constituent components. Two types of control unit implementation, namely, hardwired approach and microprogrammed approach, have been explained. Horizontal microprogramming and vertical microprogramming have been studied separately, taking into account the issues related to the microinstruction design of each one. The concept of nano programming and its implications have been narrated.
