Abstract: A bus structure for interconnecting the modules of an industrial automation controller includes DATA lines and associated control lines that enable interface circuits on each module to transfer frames of data. Modules connected to the bus structure support data transfers of differing widths and differing speeds, and interface circuits within each module automatically adapt to data width and speed differences between communicating modules. During a first bus cycle of each transfer, sending and receiving modules negotiate a bus width and clock speed to be used for the transfer by asserting their respective width and speed codes onto a set of wired-or status lines. After the first bus cycle, the status lines are then used for communicating alternate functions between the participating modules.

Abstract: A bus structure for interconnecting the modules of an industrial automation controller includes DATA lines and associated control lines that enable interface circuits on each module to send and receive frames of data. An arbitration circuit in each module employs arbitration lines in the bus structure to conduct a two phase competition to determine which module receives the next bus mastership. The arbitration lines include a set of wired-or weight code lines and a single arbitration strobe line. Modules desiring control of the bus structure assert a local weight code onto the weight code lines and determine which module is asserting the numerically greatest local weight code. Arbitration is conducted separately on the bus structure and a winning module is ready to transfer its data frame as soon as the previous winner completes its transfer and relinquishes control of the bus structure.

Abstract: A method of providing a standard coordinated time throughout spatially separated functional modules of an industrial controller employs a module operating as a time master which transmits a coordinated time to various dependent modules through communication modules. The dependent modules have local clocks which are synchronized to the coordinated time value by adjusting their clock frequency according to the difference between local time provided by that clock and the coordinated time value. This gradual correction prevents lost count values and disruption to the control process. The most and least significant bits of the time value may be transmitted at separate rates to reduce link traffic.

Abstract: A node adapter chip for linking a node microprocessor to a serial data link incorporates a read/write circuit and an interrupt processing means to allow increased flexibility in connecting the adapter to different node microprocessors with different interface protocols. The read/write input circuit accepts dual strobe or single strobe type read/write commands and the interrupt processor accepts either conventional interrupt handling or "polled" operation for use with microprocessors that do not have interrupt capabilities. A flag multiplexer allows the controller in the node adapter to receive status information from a serial interface in the adapter without the need for extra data transfer cycles.

Abstract: The I/O modules for an industrial control processor are connected together in a serial I/O ring. The processor performs an I/O scan sequence in which output data for the I/O modules is shifted serially from an output image table onto the I/O ring and input data from the I/O modules is pushed around the I/O ring and into the processor where it updates an input image table. Each I/O module can be configured to perform digital filtering and input pulse catching on the inputs and to enable a watchdog timer. Configuration data is sent out from the processor like output data and is latched into a configuration latch in the I/O module by a configure command from the processor.

Abstract: The I/O modules for an industrial control processor are connected together in a serial I/O ring. The processor performs an I/O scan sequence in which output data for the I/O modules is shifted serially from an output image table onto the I/O ring and input data from the I/O modules is pushed around the I/O ring and into the processor where it updates an input image table.