Function code Content Function description
0x03
Reading register Reads register values.
Writing register
Writes a (single) set value.
Writing complex register Writes a (complex) set value.
0x06
0x10
Communication frame structure
Name
Number of bytes Default interval
1 1
n
1 2 3 4 65
Start Machine address Function code Data Check code End
Default interval
2
Start: Set a default range of 3.65 ms or more between signals (without communication time).
Machine address: Specify a machine address to connect the RS485 module. (Refer to “List of the machine
addresses” for the setting method.)
Function code:
1
2
3
4
5
6
Data: The composition of the data section varies with the function code and register address.
(Refer to “Cases of Setting Communication Framework”.)
Check code: The calculated value of a 16-bit CRC in the Modbus-RTU mode.
End: Set a default range of over 3.65 ms between signals (without communication time).
·For CRC calculation, refer to below:
■Below is a list of register addresses used by the RS485 module for communication.
Register
address
Data name
Function
code
Type Data value
Read/
Write
Data length
[Byte]
0xFF: set Skip (keep the current setting)
Running state
UINT16
R/W
0x03
0x06
0x10
0x0001
0x00: OFF
0x01: ON
2
0xFF: set Skip (keep the current setting)
Running mode
UINT16
R/W
0x03
0x06
0x10
0x0002
0x00: Heat exchange
0x01: Normal ventilation
2
RS485 CONNECTION SETTINGS
LIST OF REGISTER ADDRESSES
8
1. Preset a 16-bit register as 0FFFFH (all 1s), which is called a CRC register.
2. Perform an exclusive-or (XOR) operation between the 8 bits of the first byte in the data
frame and the low byte in the CRC register, and store the result back to the CRC register.
3. Shift the CRC register one bit to the right, put a 0 in the most significant bit, shift out the
least significant bit, and perform a detection.
4. If the least significant bit is 0: repeat Step 3 (for the next bit shift); if the least significant
bit is1: perform an exclusive-or (XOR) operation between the CRC register and the preset
fixed value (0A001H).
5. Repeat Steps 3 and 4 until 8 bit shifts are performed. This completes the bit manipulation
of an 8-bit byte.
6. Repeat Steps 2 through 5 to manipulate the next 8 bits until all byte manipulations are
complete.
7. The final value of the CRC register is the CRC value.
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