Modbus Best Practices For Ethernet; Modbus Best Practices For Serial - Siemens 9810 Series User Manual

Communications
Key terms

Modbus best practices for Ethernet

Modbus best practices for serial

7EN05-0390-00
Term
Modbus gateway
Modbus master
Modbus RTU
Modbus register/address
Modbus slave
Modbus TCP
Modbus unit ID
You can download your device's Modbus map from www.usa.siemens.com/pds
and get additional information about the Modbus protocol from www.modbus.org.
In order for your meter to operate as an Ethernet Modbus device, you must
complete some prerequisite configuration.
NOTE: You do not need to perform any Modbus-specific configuration for your
meter to function as a Modbus slave device over Ethernet.
Prerequisite Description
Ethernet All devices must have a working Ethernet connection.
IP address All devices must have a unique IP address.
Port All devices must be communicating over Ethernet port 502 for Modbus TCP.
NOTE: Devices supporting multiple simultaneous Modbus TCP connections
can have communications delays. Adjust your network timeout settings to
accommodate this.
In order for your meter to operate as a serial Modbus device, you must complete
some prerequisite configuration.
Prerequisite Description
Wiring The device's serial connection must be wired correctly.
The Modbus slave devices must have communications wiring to the Modbus
master.
Protocol Slave: for your meter to be a serial Modbus slave, the meter's protocol must be
set to Modbus RTU. Master and slave devices must use the same format.
Master: for your meter to be a serial Modbus master, the meter's protocol must
be set to Modbus Master.
Baud rate The baud rate must be the same for all devices on the serial Modbus network.
Stop bits and The communication stop bits and parity (for example, 8N1) must be the same
parity for all devices on the serial Modbus network.
Unit ID Each device on the serial Modbus network must have a unique unit ID (also
called the device address).
Definition
A communications method that lets you communicate through an
Ethernet gateway device to a Modbus serial network connected to
that device.
A device that issues commands and receives responses from
Modbus slave devices. Serial Modbus networks can only have one
Modbus master per network.
Serial Modbus protocol format; Modbus RTU transmits data using
binary. Master and slave devices must use the same format.
Identifies the data to read/write. Modbus register maps are available
for Modbus slave devices and detail the information available from
the slave device. More than one register may be used to store a
single value.
A device that responds to Modbus commands and performs actions
or provides information back to the Modbus master. Most Modbus
networks contain multiple slave devices.
The Ethernet Modbus protocol format.
The identifier for a slave Modbus device.
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