Appendix I
124
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 :
Time interval of 3.5characters
Communication address: 1 to 247
03: Read slave parameters；06: write slave parameters
Data content: Address of function code parameter, numbers of
function code parameter, value of function code parameter, etc.
Detection Value:CRC value.
Time interval of 3.5characters
CMD (C
ommand
) 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
Number of registers high-order
Number of registers low-order
Slave responding information
When F9.05 is set to 0:
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