79
Should Modbus Slave (power meter) receive an abnormal Request, the format of the abnormal packet
responded is as follows. Refer to Chapter 9 for the abnormal codes.
Slave Response
0x01 0x83 0x1 CRC
9.3.3 User-defined Communication Protocol for Data Log Reading
(1) Take an approach similar to Modbus RTU mode. The Modbus Master sends out Request using
Function Code 0x03, which requests the Slave to response the value of the corresponding Modbus
address. The Modbus Slave will provide the value through Response.
Example:
If a Modbus Master (such as PLC or data collector) uses a user-dened communication protocol to read
the data log, the address is 0x0800. The packet format of Request sent by Modbus Master is as follows
(Similar as Modbus RTU, but the Number of Points can only be 1):
Master Request
0x01 0xFE 0x08 0x00 0x00 0x01 CRC
Slave Address Function Code
Start Address
(Hi)
Start Address
(Lo)
Numbers of
Points (Hi)
Numbers of
Points (Lo)
The packet format of Response responded by Modbus Slave (Power Meter) is as follows: (Similar to
Modbus RTU before Byte Count. The only difference is that the data is a sting of Log data, and the
sequence is as listed as follow. The total size is 66 bytes.)
Slave Response
0x01 0xFE 0x42 56 ...... 12 CRC
Slave Address Function Code
Exception Code
Slave Address Function Code
Byte Count Data Log
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