Goodrive270 series VFD for fan and pump Communication
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For example, if the master reads two contiguous pieces of data (that is, to read content from the data
addresses 0004H and 0005H) from the VFD whose address is 01H, the frame structures are
described in the following.
RTU master command (from the master to the VFD)
T1-T2-T3-T4 (transmission time of 3.5 bytes)
T1-T2-T3-T4 (transmission time of 3.5 bytes)
The value in START and END is "T1-T2-T3-T4 (transmission time of 3.5 bytes)", indicating that the
RS485 needs to stay idle for at least the transmission time of 3.5 bytes. An idle time is required to
distinguish on message from another to ensure that the two messages are not regarded as one.
"ADDR" is "01H", indicating that the command is sent to the VFD whose address is 01H. The ADDR
information occupies one byte.
"CMD" is "03H", indicating that the command is used to read data from the VFD. The CMD
information occupies one byte.
"Start address" means reading data from the address and it occupies two bytes with the MSB on the
left and LSB on the right.
"Data count" indicates the count of data to be read (unit: word). "Start address" is "0004H" and "Data
count" is 0002H, indicating that data is to be read from the data addresses of 0004H and 0005H.
CRC check occupies two bytes, with the LSB on the left, and MSB on the right.
RTU slave response (from the VFD to the master)
START
T1-T2-T3-T4 (transmission time of 3.5
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