8: Configuring Modbus/BSAP | 8 |
•Configuring the Raven at the Polling Host for Modbus on UDP
•Configuring the Remote Ravens for Modbus with UDP
The Raven supports Modbus ASCII, Modbus RTU, BSAP, and can also emulate other protocols like DF1 or others using its Modbus Variable feature.
Modbus Overview
The Modbus Protocol, developed by Modicon in 1979, provides for client‐server (also referred to as master‐slave) communications between intelligent devices. As a de facto standard, it is the most widely used network protocol in the industrial manufacturing environment to transfer discrete/ analog I/O and register data between control devices. Modbus, BSAP, and other Modbus variations are often used in conjunction with telemetry devices.
Tip: This section is just a brief overview of Modbus. For more infor- mation, refer to your Modbus equipment distributor or manufacturer or http://www.modbus.org.
Telemetry
Telemetry is an automated communications process by which data is collected from instruments located at remote or inacces‐ sible points and transmitted to receiving equipment for measurement, monitoring, display, and recording. Trans‐ mission of the information may be over physical pairs of wires, telecommunication circuits, radios or satellite.
Remote Terminal Unit (RTU)
Modbus was originally designed to be used in a radio environment where packets are broadcast from a central station (also called master or host) to a group of remote units. Each remote unit, Remote Terminal Unit (RTU), has a hexidecimal identification number (ID). The first part of the broadcast packet contains an RTU ID which corresponds to the ID of one of the remote units. The Modbus host looks for the ID and sends to only the unit with the matching ID. The RTU would then reply back to the central station.
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