Sierra Raven EDGE - Manual (Page 64)

Raven EDGE
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The RTU connects to physical equipment such as switches,
pumps, and other devices and monitors and controls these
devices. The RTU can be part of a network set up for Super‐
visory Control and Data Acquisition.
Supervisory Control and Data Acquisition (SCADA)
Supervisory Control and Data Acquisition (SCADA) describes
solutions across a large variety of industries and is used in
industrial and engineering applications to monitor and control
distributed systems from a master location. SCADA encom‐
passes multiple RTUs, a central control room with a host
computer (or network), and some sort of communication infra‐
structure.
SCADA allows for “supervisory” control of remote devices as
well as acquiring data from the remote locations. Program‐
mable Logic Controllers allow for a higher degree of
automated SCADA.
Programmable Logic Controller (PLC)
A Programmable Logic Controller (PLC) is a small industrial
computer which generally monitors several connected sensor
inputs and controls attached devices (motor starters, solenoids,
pilot lights/displays, speed drives, valves, etc.) according to a
user‐created program stored in its memory. Containing inputs
and outputs similar to an RTU, PLCs are frequently used for
typical relay control, sophisticated motion control, process
control, Distributed Control System and complex networking.
Modbus TCP/IP
Modbus TCP/IP simply takes the Modbus instruction set and
wraps TCP/IP around it. Since TCP/IP is the communications
standard for the Internet and most networked computers, this
provides a simpler installation. Modbus TCP/IP uses standard
Ethernet equipment.
Raven Modbus on UDP
When Sierra Wireless AirLink modems are used in place of
radios, a Raven is connected to the central station (host) and
aRaven is connected to each remote unit. When the Raven is
configured for Modbus with UDP, the Raven connected to the
host can store a list of IP addresses or names with matching
IDs. When the host at the central station sends serial data as a
poll request, the Raven at the host matches the RTU ID to a
corresponding IP of a Raven at a remote unit. A UDP packet is
assembled encapsulating the RTU ID and serial data trans‐
mitted from the host. The UDP packet is then transmitted to
the specific Raven at the remote unit matching the RTU ID.