Allen-Bradley Company, LLC

Timothy J Murphy

Mark Luboski

Kendal R Harris

William Edward Floro

Robert C Weppler

Margarita M Hutz

Jack D Calderon

Alan C Cribbs

Odo J Struger

Alan J Campbell

Dennis J Dombrosky

David A Karpuszka

Thaddeus A Weber

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. The interface circuit includes a flow control circuit for managing resources within the receiving module, and thus controlling the flow of data over the backplane bus. As soon as a message begins to be received, the flow control circuit makes a determination as to the availability of resources within the module to successfully receive the data frame. If sufficient resources are not available, a busy indication is returned to the transmitting module, and the transmitting module then aborts the transmission. The factors evaluated by the interface circuit in forming the determination as to the availability of resources includes the factors of: (a) availability of a control block when the frame begins a new complete message, (b) completion of processing for a frame from a particular source module before accepting another frame from that module, and (c) availability of a buffer for receiving the frame.

System having a plurality of frame bytes capable of identifying

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.

Backplane data transfer technique for industrial automation controllers

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. The winning weight code identifies both the source address of the winning module and the priority of the data frame to be sent, and is latched by all modules on the backplane bus as an arbitration vector to provide advance identification of the next module to transmit and the priority of the message.

Method for and apparatus for operating a local communications module in

A DC input circuit provides a digital output dependent on an input voltage spanning a low range and a high range. A first transistor current source provides a bounded leakage current for a low range voltage. A parallel transistor current source in series with a voltage breakdown diode provides a second constant current path for high range voltages through a current sensitive switch. The total input current is thus limited, thereby reducing heat dissipation.

DC input circuit with controlled leakage current

An inter-processor communication module is inserted into a slot of an equipment rack of the type used to connect I/O modules to system processors in a programmable controller. Using two of the inter-processor communication modules in two respective racks, a supervisory processor is connected to two respective local area processors in a distributed control system. The inter-processor communication module has a serial channel controller that connects to the supervisory processor through a serial I/O port and a serial communication channel to communicate blocks of I/O status data. The serial channel controller is coupled to a backplane controller through a common memory and arbitration circuitry to exchange blocks of I/O status data. The backplane controller, which is also a part of the inter-processor communication module, plugs into the backplane of the rack and exchanges blocks of I/O status data with a local area processor. The two controllers also exchange processor status data to coordinate communications which are initiated by the supervisory processor and the local area processor. Methods of transferring I/O status data between the supervisory processor and the local area processors are also disclosed.

Method and apparatus for linking processors in a hierarchical control

The capacity of programmable controllers with a processor module and I/O modules connected in a single equipment rack is expanded by connecting an I/O expansion module in one of the positions normally occupied by a conventional I/O module. The I/O expansion module communicates with the processor module through the rack backplane and also communicates with other racks of I/O modules and with node I/O modules through a serial data channel. Data for I/O modules on the serial data channel are stored in a bulk storage area in the processor module to expand the effective size of an image table of I/O status data that is maintained by the processor module. The processor module is programmed to operate with a backplane controller in the I/O expansion module to transfer data in or out of the bulk storage area. Besides the backplane controller, the I/O expansion module includes a serial channel controller, a common memory and arbitration circuity which allows the controllers to alternate access to the common memory and to exchange data. The serial channel controller controls multiplexing and demultiplexing of I/O status data with the I/O modules through the serial data channel.

Programmable controller with I/O expansion module located in one of I/O

A method and apparatus for access to a programmable controller at a remote location. A peripheral device with a peripheral processor is connected to a port on an I/O module. Blocks of discrete and block transfer data are transferred to and from a common memory in the I/O module where the data is accessible to a serial communication controller that interfaces the module to a high speed serial data channel. Asynchronous communication is provided between the serial communication controller and the peripheral device using a circular buffer in the common memory. Timing considerations are also disclosed.

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Hudson, OH, United States of America

Timothy J Murphy