Savch S3100A Series, User Manual

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RTU Frame format:
Frame header (START) 3.5 character time
Slave address (ADR) Communication address:1~247
Command code (CMD)
03: Read slave parameters;
06: Write slave parameters
DATA(N-1)
Data content: Function code parameter address,
function code parameter number, function code
parameter value, etc.
DATA(N-2)
……
DATA 0
CRC CHK upper bite
Detection value: CRC value
CRC CHK lower bite
END 3.5 character time
Command code and communication data description:
Command code: 03H, read N words (Word can read up to 12 words)
For example: the start address 0002 of the inverter with slave address 01 is continuously reading two consecutive
values.
RTU host command information RTU slave response information
ADR 01H ADR 01H
CMD 03H CMD 03H
Start address upper bit 00H Byte number 04H
Start address lower bit 02H Date address 0002H upper bit 00H
Date number upper bit 00H Date address 0002H lower bit 00H
Date number lower bit 02H Date address 0003H upper bit 00H
CRC CHK lower bit
CRC CHK
Date address 0003H lower bit 01H
CRC CHK upper bit CRC CHK Lower bit
CRC CHK
CRC CHK Upper bit