Thermo Scientific 146i, Instruction Manual

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MODBUS Protocol
TCP Communication Parameters
C-2 Model 146 i Instruction Manual Thermo Fisher Scientific
i
Series Instruments support the MODBUS/TCP protocol. The register
definition is the same as for the serial interface.
TCP connection port for MODBUS : 502
Here are the MODBUS ADU (Application Data Unit) formats over serial
and TCP/IP:
Serial: Slave Address Function Code Data Error Check
TCP/IP: MBAP Header Function Code Data
The MODBUS save address is a single byte in length. This is the same as
the instrument ID used for C-Link commands and can be between 1 and
127 decimal (i.e. 0x01 hex to 0x7F hex). This address is only used for
MODBUS RTU over serial connections.
Note
Device ID ‘0’ used for broadcast MODBUS commands, is not
supported. Device IDs 128 through 247 (i.e. 0x80 hex to 0xF7 hex) are not
supported because of limitations imposed by C-Link.
▲
In MODBUS over TCP/IP, a MODBUS Application Protocol Header
(MBAP) is used to identify the message. This header consists of the
following components:
Transaction Identifier 2 Bytes 0x0000 to 0xFFFF (Passed back in response)
Protocol Identifier 2 Bytes 0x00 (MODBUS protocol)
Length 2 Bytes 0x0000 to 0xFFFF (Number of following bytes)
Unit Identifier 1 Byte 0x00 to 0xFF (Passed back in response)
A Slave address is not required in MODBUS over TCP/IP because the
higher-level protocols include device addressing. The unit identifier is not
used by the instrument.
TCP Communication
Parameters
Application Data
Unit Definition
Slave Address
MBAP Header