Powtran PI9000 series - Page 232

Appendix I
226
result in an error, because the value in the final CRC field is not right.
RTUframe format :
Frame header START
Time interval of 3.5characters
Slave address ADR
Communication address: 1 to 247
Command code CMD
03: read slave parameters；06: write slave parameters
Data content DAT A(N-1)
Data content: address of function code parameter, numbers of
function code parameter, value of function code parameter, etc.
Data content DAT A(N-2)
………………………
Data content DAT A0
CRC CHK high-order
Detection Value: CRC value.
CRC CHK low-order
E ND
Time interval of 3.5characters
CMD (Command) and DATA (data word description)
Command code: 03H, reads N words (max.12 words), for example: for the inverter with slave
address 01, its start address F0.02 continuously reads two values.
Master command information
ADR
01H
CMD
03H
Start address high-order
F0H
Start address low-order
02H
Number of registers high-
order
00H
Number of registers low-
order
02H
CRC CHK low-order
CRC CHK values are to be calculated
CRC CHK high-order
Slave responding information
When F9.05 is set to 0:
ADR
01H
CMD
03H
Byte number high-order
00H
Byte number low-order
04H
Data F002H high-order
00H
Data F002H low-order
00H
Data F003H high-order
00H
Data F003H low-order
01H
CRC CHK low-order
CRC CHK values are to be calculated
CRC CHK high-order