ABSTRACT
A completely new customized program has to be developed, which requires much microprocessor programming skill and which increases the overall cost of implementation. The power of the arrangement can be enhanced by dedicating one read-only memory (ROM) to hold the control program and interrupt handling routines, dedicating another ROM to store the output control table, and dedicating a third ROM to storing the next state sequence table. The controller then becomes very flexible. The basic problem in sequence control is to activate the control signals that drive a process in a controlled manner. The flow of control could depend on the feedback from the rest of the plant. The complete diagram can be considered a collection of state sequence blocks in which each state sequence block is associated with one and only one state sequence indicated by a box.
