CT100 inverter Communication protocol
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The master refers to a personal computer (PC), an industrial control device or a
programmable logic controller (PLC), etc. The slave is CT100 inverter. The
master can communicate with a single slave as well as send a broadcast
message to all slaves. For the master’s single "query/command", the slave has
to return a message (called a response), for the master’s broadcast message,
the slaves do not need to respond to the master.
5. Communication data format
The Modbus protocol communication data format of CT100 series inverters is as
follows:
In RTU mode, the minimum interval time should be at least 3.5 bytes for
message transmission, which is the easiest way to achieve a variety of character
time at the baud rate. The first transmitted field is the device address. The
transmitted characters can be hexadecimal 0...9 and A...F. The network device
constantly detects the network bus, even during the interval time. When the first
field (address field) is received, the corresponding device decodes next
transmitting character. After the last transmitting character, the interval time of at
least 3.5 bytes marks the end of the message. A new message can start after this
pause.
The whole message frame is a continuous transmitting flow. If there is an interval
time of more than 1.5 bytes before the frame is completed, the receiving device
will renew the uncompleted message and assume that the next byte is the
address field of a new message. As such, if the new message follows the
previous message within the interval time of 3.5 bytes, the receiving device will
deal with it as the same with the previous message. If these two phenomena all
happen during the transmission, the CRC will generate a fault message to
respond to the sending devices.
Interval time of 3.5 bytes
Communication address: 1～247
03: read slave parameters; 06: write slave
parameters
Function parameter address, function parameter
number, function parameter value etc.
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