FOTEK GD20-004G-2, Operation Manual

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Goodrive20 Series VFD Communication protocol
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1
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15
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32
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6
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Maincontrol
devices
Figure 7-3 Star connection
Use shielded cables, if possible, in multi-VFD connection. The baud rates, data bit check
settings, and other basic parameters of all the devices on the RS485 line must be set
consistently, and addresses cannot be repeated.
7.2.2 RTU mode
7.2.2.1 RTU communication frame structure
When a controller is set to use the RTU communication mode on a Modbus network, every
byte (8 bits) in the message includes 2 hexadecimal characters (each includes 4 bits).
Compared with the ASCII mode, the RTU mode can transmit more data with the same baud
rate.
Code system
•
1 start bit
•
7 or 8 data bits; the minimum valid bit is transmitted first. Each frame domain of 8 bits
includes 2 hexadecimal characters (0
–9, A–F).
•
1 odd/even check bit; this bit is not provided if no check is needed.
•
1 stop bit (with check performed), or 2 bits (without check)
Error detection domain
•
Cyclic redundancy check (CRC)
The following table describes the data format.
11-bit character frame (Bits 1 to 8 are data bits)
Start bit BIT1 BIT2 BIT3 BIT4 BIT5 BIT6 BIT7 BIT8 Check bit Stop bit
10-bit character frame (Bits 1 to 7 are data bits)
Start bit BIT1 BIT2 BIT3 BIT4 BIT5 BIT6 BIT7 Check bit Stop bit
In a character frame, only the data bits carry information. The start bit, check bit, and stop bit
are used to facilitate the transmission of the data bits to the destination device. In practical