Sierra Wireless RAVEN 1X 20070914 - Manual (Page 82)

Rev 3.0B Feb.08 77
8 8: Configuring Modbus/BSAP
• 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.