Input/output (I/O) scanner for a control system with peer determination
First Claim
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1. A method comprising the steps of:
- providing a first device on a first node of a communications network, the first device configured to connect to and scan I/O devices;
providing a second device on a second node of the communications network, the second device configured to connect to and scan the I/O devices;
assigning a first address to a the first node and a second address to a the second node, wherein the first address is characteristic of a primary mode of operation;
initiating from the first node a first communications command in a peer protocol format addressed to the second node;
initiating from the second node a second communications command in the peer protocol format addressed to the first node;
identifying the second device on the second node as a peer device within the first device on the first node responsive to receiving the second communications command at the first node;
identifying the first device on the first node as a peer device within the second device on the second node responsive to receiving the first communications command at the second node;
wherein the peer device is a programmable logic controller (PLC) device;
scanning the I/O devices by the first device on the first node;
determining that the first node is inoperable;
initiating at the second node an exchange of the first address and the second address responsive to determining that the first node is inoperable;
resetting a connection between the first device and the I/O devices responsive to determining that the first node is inoperable; and
assigning the first address to the second node and the second address to the first node responsive to initiating the exchange.
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Abstract
A method and apparatus for providing an active standby control system includes the steps of providing a first and second programmable logic controller (PLC), each controller having an operating state. Each controller includes a network module board operably connected to a network; a control unit, a remote I/O head; and, a hot standby module, each hot standby module is operably connected together. PLC. This method and apparatus can be used within a control system for monitoring input devices and for controlling output devices which reside on the standard communications network such as an Ethernet network, and the standard communications protocol used therein can be TCP using Modbus.
97 Citations
16 Claims
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1. A method comprising the steps of:
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providing a first device on a first node of a communications network, the first device configured to connect to and scan I/O devices; providing a second device on a second node of the communications network, the second device configured to connect to and scan the I/O devices; assigning a first address to a the first node and a second address to a the second node, wherein the first address is characteristic of a primary mode of operation; initiating from the first node a first communications command in a peer protocol format addressed to the second node; initiating from the second node a second communications command in the peer protocol format addressed to the first node; identifying the second device on the second node as a peer device within the first device on the first node responsive to receiving the second communications command at the first node; identifying the first device on the first node as a peer device within the second device on the second node responsive to receiving the first communications command at the second node; wherein the peer device is a programmable logic controller (PLC) device; scanning the I/O devices by the first device on the first node; determining that the first node is inoperable; initiating at the second node an exchange of the first address and the second address responsive to determining that the first node is inoperable; resetting a connection between the first device and the I/O devices responsive to determining that the first node is inoperable; and assigning the first address to the second node and the second address to the first node responsive to initiating the exchange. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A device scanner for a first device located on a first node of a standard communications network configured to connect to and scan I/O devices on a communications network, the device scanner comprising:
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a network module for receiving a first address assigned to the first node, wherein the first address is characteristic of a primary mode of operation; an initiator for initiating a first communications command in a peer protocol format addressed to a second node; a receptor for receiving from the second node a second communications command in the peer protocol format, in response to the first communications command, and for receiving from the second node a communications command to exchange the first address with a second address assigned to the second node; and an identifier for identifying a second device on the second node as a peer device, wherein the peer device is a programmable logic controller (PLC) device, and wherein the network module is configured to reset connections from the device scanner to the I/O devices prior to exchange of the first address with the second address such that the first node is assigned the second address responsive to the exchange. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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Specification