Abstract: In an industrial controller associated with independent I/O modules for exchanging signals between a controlled machine and the controller, a control program executed by the controller is associated with an I/O map identifying functionality of the independent I/O modules. At initialization of the controller, function keys are transmitted to the I/O modules, the latter which confirm that they are capable of the functions expected by the control program. The I/O modules may change their function according to the function keys and may accept functions not identical to those performed by the I/O module if the I/O module performs at greater functionality.

Abstract: A communication network for an industrial control system permits multiple masters and complex network topologies by transmitting data as packets through paths of nodes on the networks. The packets containing data are preceded by an OPEN message which pre-configured each node with the necessary information to process the stream of succeeding packets in an efficient manner and thus to reduce the necessary overhead in the transmission of each data packet. Each node receiving the OPEN message evaluates its resources and if those resources are insufficient to reliably handle the indicated packets, a message is returned to the originating node indicating that a connection cannot be formed.

Abstract: A programmable controller includes a memory which stores an I/O image table and a data table. An I/O scanner module updates the I/O image table with the status of I/O devices connected to the programmable controller. The processor executes a control program to perform logical and arithmetic operations on the data in the data table. Such operations may be performed on data of different types and any necessary data conversions are performed automatically. Also, such operations may be performed on entire data files without degrading the response time of the programmable controller.