Fonrich FR-DCMG-MMPS, Руководство пользователя

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MODBUS Protocol Definition
Communication format configuration
•
Modbus communication mode: RTU mode
•
Address of the slave device: range form 1 to 247 (default 247)
•
Baud rate (bps): 2400, 4800, 9600 (default), 19200, 38400
•
Byte check mode: odd check, even check, no check (default)
Data frame format description (refer to Modbus RTU standard)
The byte in the communication frame composed by 1 start bit, 8 bits data bit, 1 parity bit, 1
stop bit like the below table
（
Refer to standard modbus RTU protocol):
Table 1: Data frame format table
Address Code Function Code Data Area Check Zone
1byte 1byte N*1byte 2bytes
The address code is used to identify the slave that receives the data frame and the response
frame sent by that slave. The function code indicates how the master requires the slave to
respond and the slave responds to that function code. Data area The content can be the address
value, the number of registers, the data from the slave response and the data sent by the master
to the slave, etc., which can hold up to 252 bytes of data. The check area uses CRC cyclic
redundancy to check whether a frame of data is wrong. The high byte of the data frame comes
first, and the low byte comes after.
Function code description
Register reads and writes in bits
• Function code 01 used to read the contents of the bit register
•
Function code 02 used to reads the contents of the bit register
•
Function code 05 used to write single bit-type registers
The contents represented by the register in bits are: switch value, alarm information, etc.
Register read and write in word units
•
Function codes 03
、
04 are used to read multiple word-type registers
• Function code 06 is used to write single word-type registers
•
Function code 16 is used to multiple word-type registers
The content of the word-type registers can be voltage, current, generated energy, etc