Airlink X EV-DO - Manual (Page 35)

Raven X EV-DO for Verizon - User Guide, version 2.34 29
CHAPTER 6
Modbus/BSAP Configuration
The Raven X 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/ana-
log I/O and register data between control devices.
Modbus, BSAP, and other Modbus variations are often used in conjunction with telemetry devices.
Telemetry
Telemetry is an automated communications process by which data is collected from instruments
located at remote or inaccessible points and transmitted to receiving equipment for measurement,
monitoring, display, and recording. Transmission 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.
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.
This section is just a brief overview of Modbus. For more information, refer to
your Modbus equipment distributor or manufacturer or http://www.modbus.org.