Sourcetronic ST500 004G1, Руководство пользователя

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Appendix I
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The allowable characters for transmitting are hexadecimal 0 ... 9, A ... F. The networked devices
continuously monitor network bus, including during the silent intervals. When the first field (the
address field) is received, each device decodes it to find out if it is sent to their own. Following the
last transmitted character, a silent interval of at least 3.5 characters marks the end of the message. A
new message can begin after this silent interval.
The entire message frame must be transmitted as a continuous stream. If a silent interval of more
than 1.5 characters occurs before completion of the frame, the receiving device will flushes the
incomplete message and assumes that the next byte will be the address field of a new message.
Similarly, if a new message begins earlier than the interval of 3.5 characters following a previous
message, the receiving device will consider it as a continuation of the previous message. This will
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 DATA(N-1)
Data content: address of function code parameter, numbers of
function code parameter, value of function code parameter, etc.
Data content DATA(N-2)
………………………
Data content DATA0
CRC CHK high-order
Detection Value: CRC value.
CRC CHK low-order
END
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 01H
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
When F9.05is set to 1:
ADR 01H
CMD 03H
Byte number 04H