About Modbus
Modbus is a very common protocol used in data acquisition and control
applications. Note however that just because some device supports Modbus,
it doesn’t mean it automatically works with any other Modbus device.
The ezeio has support for over 50 different types of devices. Contact us for
the complete list and to explore adding support do devices not already on the
list.
Every Modbus network requires one ‘master’ and one or more ‘slave’
devices. The master device will send out periodic questions, and the slave
devices will reply to those questions. Slave devices must never transmit
unless specifically requested by the master.
The ezeio is always a Modbus RTU master.
The Modbus protocol can be transported over several different physical
networks. The most common are RS-485 and Ethernet.
Modbus RTU
(a.k.a. Modbus RS-485) is a robust multi-drop serial network.
This means that all the devices connected to the network communicate over
the same pair of wires. The signal rate is typically 19200 bits per second,
which is usually more than enough for the types of devices used in ezeio
applications.
Modbus TCP/IP
use Ethernet hardware to connect the devices. The data
rate is much higher than on RS-485, but that also limits the range (typically
to 100m/300ft). Ethernet uses switches to which all devices needs to be
connected (star topology).
While the fundamental protocol is the same over Modbus RTU and TCP/IP,
the IP network requires additional consideration to have the data correctly
routed and correctly addressed. In common data acquisition and control
applications, Modbus TCP does not provide any functional benefit, but adds
significant complexity to the setup process.
The ezeio support Modbus RTU.
While Modbus TCP is not supported by the ezeio
™
, there are protocol
converters for Modbus TCP to Modbus RTU. Contact eze System for details.
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