Modbus TCP/IP Driver Manual
Page 4 of 23
1 MODBUS TCP/IP DESCRIPTION
The Modbus TCP Driver allows the FieldServer to transfer data to and from devices over Ethernet using
the Modbus TCP/IP Protocol. The Modbus TCP/IP driver uses port 502, which is not configurable. The
driver was developed for Modbus Application Protocol Specification V1.1a from Modbus-IDA. The
specification can be found at www.modbus.org. The FieldServer can emulate either a Server or Client.
The information that follows describes how to expand upon the factory defaults provided in the
configuration files included with the FieldServer.
There are various register mapping models being followed by various vendors.
To cover all these mappings, FieldServer uses the following three Models:
• Modicon_5digit – Use this format where addresses are defined in 0xxxx, 1xxxx, 3xxxx or 4xxxx
format. A maximum of 9999 registers can be mapped of each type. This is FieldServer driver’s
• ADU – Application Data Unit address. Use this format where addresses of each type are defined
in the range 1-65536.
• PDU – Protocol Data unit address. Use this format where addresses of each type are defined in
the range 0-65535.
An example of the key difference between ADU and PDU:
• If Address_Type is ADU and address is 1, the driver will poll for register 0.
• If Address_Type is PDU, the driver will poll for address 1.
NOTE: If the vendor document shows addresses in extended Modicon (i.e. 6 digit) format like
4xxxxx then consider these addresses as xxxxx (omit the first digit) and use either ADU or
NOTE: The purpose of providing 3 different ways of addressing the Modbus registers is to allow
the user to choose the addressing system most compatible with the address list being
used. At the protocol level, the same protocol specification is used for all three with the
exception of the limited address range for Modicon_5digit.
2 DRIVER SCOPE OF SUPPLY
2.1 Supplied by MSA Safety
UTP cable (7 foot) for Ethernet connection1
2.2 Provided by the Supplier of 3rd Party Equipment
Modbus/TCP Server, e.g. Quantum PLC 2
Modbus/TCP Host Node [such as: Intellution Fix, Wondereware Intouch, GE Cimplicity, Quantum PLC
1 This cable is necessary for connection to the driver. It is shipped with the FieldServer and not separately with the driver.
2 If FieldServer is used as a Modbus/TCP Client.
3 If FieldServer is used as a Modbus/TCP Server.