CHAPTER 8 - CFW-09 OPTIONS AND ACCESSORIES
In the RTU mode there is no specific character that indicates the beginningor
the end of a message. Thus the onlyindication for the beginning or the end of
a new message is the data transmission absence in the network by3.5 times
thetime requiredfortransmissionof one dataword (11 bits).Thusif a message
is initiated after elapsing of the minimum time required without transmission,
the network elements assume that the received character represents the
beginning of a newmessage. In similar mode, after this time has elapsed, the
network elements will assume that the message has been ended.
If during the transmission of a message, the time between the bytes is longer
than this minimum required time, the message will be considered invalid,
since the inverter willdiscard the already receivedbytes and will mounta new
message with the bytes that are being transmitted.
The table below shows the time for three different communication rates.
TheCFW-09frequencyinvertersoperateasslavesoftheModbus-RTUnetwork.
The communication initiates with the master of the Modbus-RTU network
requesting a service for a network address. When the inverter is configured to
the corresponding address, it processes the question and answers to the
The CFW-09 frequencyinverters use a serial interface for thecommunication
with the Modbus-RTUnetwork. There are twoways to perform theconnection
between the network master and the CFW-09:
- Times required during the communication of a message
Time to transmit one word of the message.
Time between bytes (can not be longer than T
Minimum interval to indicate the begin and the end of the
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