INVT GD350-004G/5R5P-45-AS, Руководство по эксплуатации

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Goodrive350 IP55 High-ingress Protection Series VFD Communication protocol
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Use shielded cable, if possible, in multi-device 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.
9.3.2 RTU mode
9.3.2.1 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 end bit (with check performed), 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 End bit
10-bit character frame (Bits 1 to 7 are data bits)
Start bit BIT1 BIT2 BIT3 BIT4 BIT5 BIT6 BIT7 Check bit End bit
In a character frame, only the data bits carry information. The start bit, check bit, and end bit
are used to facilitate the transmission of the data bits to the destination device. In practical
applications, you must set the data bits, parity check bits, and end bits consistently.
In RTU mode, the transmission of a new frame always starts from an idle time (the
transmission time of 3.5 bytes). On a network where the transmission rate is calculated based
on the baud rate, the transmission time of 3.5 bytes can be easily obtained. After the idle time
ends, the data domains are transmitted in the following sequence: slave address, operation
command code, data, and CRC check character. Each byte transmitted in each domain
includes 2 hexadecimal characters (0
–9, A–F). The network devices always monitor the
communication bus. After receiving the first domain (address information), each network
device identifies the byte. After the last byte is transmitted, a similar transmission interval (the
transmission time of 3.5 bytes) is used to indicate that the transmission of the frame ends.
Then, the transmission of a new frame starts.