Function Codes - Thermo Scientific 48i Instruction Manual

MODBUS Protocol
TCP Communication Parameters
TCP Communication
Parameters
Application Data
Unit Definition
Slave Address
MBAP Header
C-2 Model 48i Instruction Manual
iSeries instruments support the MODBUS/TCP protocol. The register
definition is the same as for the serial interface. Up to three simultaneous
connections are supported over Ethernet.
TCP connection port for MODBUS : 502
Here are the MODBUS ADU (Application Data Unit) formats over serial
and TCP/IP:
Serial: Slave Address
TCP/IP: MBAP Header Function Code
The MODBUS slave 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
Protocol Identifier 2 Bytes
Length 2 Bytes
Unit Identifier 1 Byte
Function Code Data
Data
0x0000 to 0xFFFF (Passed back in response)
0x00 (MODBUS protocol)
0x0000 to 0xFFFF (Number of following bytes)
0x00 to 0xFF (Passed back in response)
Error Check
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