Abstract: In a sequence-of-events system for a distributed process control system, unfiltered changes in process element status are initially stored at each remote site along with a time tag. Each remote site has an I/O manager board to which are connected a number of individual I/O boards. Each I/O board in turn has connected to it process signal inputs from a number of process elements (e.g., 16), which can be in an "on" or "off" state. Each I/O board includes a change-of-state detector to which the process signal inputs are coupled. The change-of-state detector detects a change of state of any process input and generates an interrupt signal, which is coupled to a microprocessor also located on the I/O board. The microprocessor reads the status of all the process element inputs coupled to the scanner and also the output of a local clock on the I/O board.

Abstract: An industrial control system is disclosed in which various on/off or other binary functions of an industrial process are each controlled by a separate single board computer. Each single board computer is provided with a simplified system whereby the user can interconnect a logic system between input ports and output ports of the computer to control the setting of the binary data at the output ports in accordance with the selected logic system in response to the data applied to the input ports with the output ports being connected to control the on/off and binary functions in the system. The logic functions are implemented in each single board computer by use of an applications program and a patch panel program. In the applications program, the system responds to input data in a flag memory and sets output flags in the flag memory in accordance with each possible logic function that might be used in the system.

Abstract: An industrial control system in accordance with the present invention is provided with a plurality of diverse controlled devices (e.g., fans, pumps, valves, solenoids, relays, etc.) for effecting overall system control. Each device has a unique set of logic control functions and/or command sequences and is connected, through an input/output interface, to a stored-program single board computer that provides device control and monitoring. The computers each include a central processor controlled by a composite or "master" program which is common to all the computers and which includes instruction sequences for all logic control functions and command sequences that exist within the system. A user alterable interconnection device (UAID) permits only those logic control function and/or command sequence portions of the master program that relate to a particular one of the controlled devices to operatively connect with the particular input/output ports associated with that controlled device.