CS Instruments DS 400 User Manual

DS 400 Side 7 of 36
3.3.1 Serial transmission modes (RTU)
The DS 400 Modbus mode support only one serial transmission modes; the RTU
mode. The transmission mode defines the bit contents of message fields
transmitted serially on the line. It determines how information is packed into the message
fields and decoded.
The transmission mode and serial port parameters must be the same for all devices on a
Modbus serial line.
RTU mode Modbus Application Data Unit (ADU) frame is shown below, and is valid for
both requests and responses
Slave address
Function code
Data
CRC
1 byte
1byte
0 up to 252 byte(s)
2 bytes
Tabelle 1
Further details of the Modbus protocol can be found in Reference 1 and 2.
3.3.2 Ethernet transmission modes
The DS 400 Modbus mode supports the Modbus/TCP only
The transmission mode defines the bit contents of message fields transmitted serially on the
line. It determines how information is packed into the message fields and decoded.
The transmission mode and serial port parameters must be the same for all devices on a
Modbus serial line.
Modbus/TCP mode Modbus Application Data Unit (ADU) frame is shown below, and is
valid for both requests and responses
Modbus/TCP MBAP Header
PDU
Transaction
Id
Protocol
Id
Length
Unit Id
Function
Code
Data
2 byte
2 byte
2 byte
1 byte
1byte
0 up to 252 byte (s)
Tabelle 2

CS Instruments DS 400 Specifications

General

Brand	CS Instruments
Model	DS 400
Category	Measuring Instruments
Language	English