Modbus Protocol - Woodward easYgen-2000 Series User Manual

7.6

Modbus Protocol

Address range
37535B
Modbus is a serial communications protocol published by Modicon
in 1979 for use with its programmable logic controllers (PLCs). It
has become a de facto standard communications protocol in
industry, and is now the most commonly available means of con‐
necting industrial electronic devices. The Woodward controller sup‐
ports a Modbus RTU Slave module. This means that a Master
node needs to poll the controller slave node. Modbus RTU can
also be multi-dropped, or in other words, multiple Slave devices
can exist on one Modbus RTU network, assuming that the serial
interface is a RS-485.
Detailed information about the Modbus protocol is available on the
following website:
http://www.modbus.org/specs.php
n
There are also various tools available on the internet. We recom‐
mend using ModScan32 which is a Windows application designed
to operate as a Modbus Master device for accessing data points in
a connected Modbus Slave device. It is designed primarily as a
testing device for verification of correct protocol operation in new or
existing systems.
A trial version download is available from the following website:
http://www.win-tech.com/html/modscan32.htm
n
The controller Modbus Slave module distinguishes between visual‐
ization data and configuration & remote control data. The different
data is accessible over a split address range and can be read via
the "Read Holding Register" function.
Furthermore, controller parameters and remote control data can be
written with the "Preset Single Registers" function or "Preset Mul‐
tiple Registers" (Fig. 248)
Fig. 248: Address range
easYgen-2200/2500 | Genset Control
Interfaces And Protocols
Modbus Protocol
467