Instructions

Basic Operation 25
Doc: HMSI-27-314, Rev. 3.10Anybus Communicator EtherNet/IP / Modbus-TCP User Manual
2.5 Modbus-TCP
2.5.1 General
The Modbus-TCP protocol is an implementation of the standard Modbus protocol running on top of
TCP/IP. The built-in Modbus-TCP server provides access to the input and output data areas via a sub-
set of the functions defined in the Modbus-TCP specification.
The server supports up to 8 simultaneous connections and communicates over TCP port 502. For de-
tailed information regarding the Modbus-TCP protocol, consult the Open Modbus Specification.
2.5.2 Addressing Modes
The Anybus Communicator features two different modes of operation regarding the Modbus commu-
nication:
• Modbus Addressing Mode (Default)
In this mode, the input and output data areas are mapped to different function codes.
Note that coil addressing is not possible in this mode.
See also...
- “Modbus Addressing Mode” on page 26
• Anybus Addressing Mode
Compared to Modbus Addressing Mode, this mode allows data to be addressed in a more flexible
way. Note however that several function codes can be used to access the same data in the gate-
way. While this may appear confusing at first, it allows data to be manipulated in ways not pos-
sible in Modbus Addressing Mode (e.g. it is possible to manipulate individual bits of a register by
accessing coils associated with the same memory location).
See also...
- “Anybus Addressing Mode” on page 27
2.5.3 Supported Exception Codes
Code Name Description
0x01 Illegal function The function code in the query is not supported
0x02 Illegal data address The data address received in the query is outside the initialized memory area
0x03 Illegal data value The data in the request is illegal