Serial Communication Parameters; Tcp Communication Parameters; Application Data Unit Definition; Slave Address - Thermo Scientific 49i Instruction Manual

MODBUS Protocol

Serial Communication Parameters

Serial Communication
Parameters
TCP Communication
Parameters
Application Data Unit
Definition

Slave Address

MBAP Header

C-2 Model 49i Instruction Manual
The following are the communication parameters that are used to configure
the serial port of the iSeries to support MODBUS RTU protocol.
Number of Data bits : 8
Number of Stop bits : 1
Parity
Data rate
iSeries 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
TCP/IP: MBAP Header
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
: None
: from 1200-115200 Baud (9600 is default)
Function Code
Function Code
0x0000 to 0xFFFF (Passed back in response)
0x00 (MODBUS protocol)
0x0000 to 0xFFFF (Number of following bytes)
0x00 to 0xFF (Passed back in response)
Data Error Check
Data
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