Nidec LEROY-SOMER Powerdrive FX, Руководство по вводу в эксплуатацию

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OPERATION WITH MODBUS RTU
Commissioning manual Powerdrive MD2/FX
4617 en - 2017.09 / e
6.4.7 - Wait time
In MODBUS RTU, when the master sends a message to a
slave, it imposes a wait time between the end of its request and
the start of the response from the slave, which makes it possible
to detect any missing response.
6.4.8 - Exceptions
If the message is incorrect and the frame is not received, or if
the CRC trips, the slave will not produce an exception, and in
this case the master will not receive a response from the slave
(«timeout»). If a write request (function code 16 or 23) exceeds
the maximum size accepted by the slave, then the slave will
reject the message. No exception will be transmitted and the
master will not receive a response.
6.4.9 - CRC
This check word is used to detect transmission errors. It is
calculated over 16 bits from all the bytes in the question and
response frames.
Algorithm:
START
CRC = 0xFFFF
Number of bytes processed = 0
Next byte = first byte
REPEAT
{
Byte to be processed = next byte;
CRC = CRC XOR byte to be
processed
REPEAT eight times
{
IF (CRC odd) then
CRC = CRC/2 XOR
0xA001
else
CRC = CRC/2
}
Number of bytes processed = Number of
bytes pro 1
}
WHILE (Number of bytes processed <
Number of bytes to be processed)
END.