Vicruns 2S-0.4G-B, User Manual

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Chapter 10 Appendix
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5.Communication frame structure
The Modbus protocol communication data format of KD600 series inverter is as follows.
Using RTU mode, message transmission starts with a pause interval of at least 3.5 character
times. This is the easiest to implement with various character times at the network baud rate
(as shown in T1-T2-T3-T4 in the figure below). The first field of the transfer is the device ad-
dress. The transfer characters that can be used are 0...9,A...F in hexadecimal. The network
device continuously detects the network bus, including the pause interval. When the first field
(address field) is received, each device decodes it to determine whether it is destined for its
own. After the last transmitted character, a pause of at least 3.5 character times marks the
end of the message. A new message can start after this pause.
The entire message frame must be transmitted as a continuous stream. If there is a pause of
more than 1.5 character times before the frame is complete, the receiving device will flush
the incomplete message and assume the next byte is the address field of a new message.
Likewise, if a new message follows the previous message in less than 3.5 characters, the
receiving device will consider it a continuation of the previous message. This will cause an
error because the value in the final CRC field cannot be correct.
Modbus
RTU Data Frame Format
Start:
at least
3.5-byte
internal time
Slave
Function
code
Data
Check
Stop:
at least
3.5-byte
internal time
RTU frame format:
Frame header START 3.5 character time
Slave address ADR Communication address: 1
～
247 (set by P8-02)
Command code CMD 03: Read slave parameters; 06: Write slave parameters
Data content DATA (N-1)
Data content:
Function code parameter address, function code
parameter number, function code parameter value, etc.
Data content DATA (N-2)
...
Data content DATA0
CRC CHK low order
Detection value: CRC16 check value. When
transmitting, the low byte comes first and the high byte
follows. For the calculation method, please refer to the
description of CRC check in this section.
CRC CHK high bits
END 3.5 character time
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