RLXIC-SV
♦
Intelligent Cellular
Configuring Modbus/BSAP
RadioLinx Intelligent Cellular Serial Modem for the Verizon Wireless CDMA Network
User Manual
Page 82 of 146
ProSoft Technology, Inc.
May 29, 2009
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 Supervisory Control and Data Acquisition.
9.1.3 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
encompasses multiple RTUs, a central control room with a host computer (or
network), and some sort of communication infrastructure.
SCADA allows for "supervisory" control of remote devices as well as acquiring
data from the remote locations. Programmable Logic Controllers allow for a
higher degree of automated SCADA.
9.1.4 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.
9.1.5 Modbus
TCP/IP
Modbus TCP/IP simply takes the Modbus instruction set and wraps TCP/IP
around it. Because 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.
9.1.6 RLXIC Modbus on UDP
When RadioLinx modems are used in place of radios, one RLXIC-SV is
connected to the central station (host) and the other RLXIC-SV is connected to
each remote unit. When the RLXIC-SV is configured for Modbus with UDP, the
RLXIC-SV 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 RLXIC-SV at the host matches the RTU ID to a corresponding IP of
a RLXIC-SV at a remote unit. A UDP packet is assembled encapsulating the
RTU ID and serial data transmitted from the host. The UDP packet is then
transmitted to the specific RLXIC-SV at the remote unit matching the RTU ID.
The remote RLXIC-SV then disassembles the packet before transmitting the
RTU ID and serial data to the remote unit. The remote units operate in normal
UDP mode, and their data is sent to the host via the remote RLXIC-SV and host
RLXIC-SV.
