Specifications

JiaXing Jarol Scientific Instrument Co.,Ltd － JR 6 000 series product s
108
7.3
7.3
7.3
7.3 Protocol
Protocol
Protocol
Protocol Format
Format
Format
Format
Modbus protocol supports both RTU. The frame f ormat is illustrated as follows:
Modbus adopts “ Big Endian ” representation for data frame. This means that when a numerical quantity
larger than a byte is transmitted, the most significant byte is sent first.
RTU
RTU
RTU
RTU mode
mode
mode
mode
In RTU mode, the Modbus minimum idle time between frames should be no less than 3.5 bytes. The
checksum adopts CRC-16 method. All data except checksum itself sent will be counted into the
calculation. Please refer to section: CRC Check for more information. Note that at least 3.5 bytes of
Modbus idle time should be kept and the start and end idle time need not be summed up to it.
The table below shows the data frame of reading parameter 002 from slave node address 1.
Node
Node
Node
Node addr.
addr.
addr.
addr. Command
Command
Command
Command Data
Data
Data
Data addr.
addr.
addr.
addr. Read
Read
Read
Read No.
No.
No.
No. CRC
CRC
CRC
CRC
0x01 0x03 0x00 0x02 0x00 0x01 0x25 0xCA
The table below shows the reply frame from slave node address 1
Node
Node
Node
Node addr.
addr.
addr.
addr. Command
Command
Command
Command Bytes
Bytes
Bytes
Bytes No.
No.
No.
No. Data
Data
Data
Data CRC
CRC
CRC
CRC
0x01 0x03 0x02 0x00 0x00 0xB8 0x44