Sequence control system

Abstract

A sequence control system suitable for checking the operation of an information processor includes a process I/O unit for receiving input data from process inputs and providing output data to process outputs; a sequence processing unit for calculating data at the process outputs by performing sequence operations according to the sequence programs stored in a sequence program memory on the basis of the data at the process inputs; a buffer memory provided between the process I/O unit and the sequence processing unit for storing both the process input data from the process I/O unit and the output data from the sequence processing unit; a control arrangement for setting the input data to the buffer memory and for allowing access to a selected sequence program according to manually set input information; a display for displaying the selected sequence program accessed through the control arrangement; and a switch for interrupting the transfer of I/O data between the process I/O unit and the buffer memory. The sequence processing unit determines the output data on the basis of the input data stored in the buffer memory and applies the output data to the buffer memory. The control arrangement, in response to the manually set input information, causes the associated sequence program to be read from the sequence program memory and then the data of the inputs and outputs associated with the sequence program to be read from the buffer memory thereby to indicate them on the display.