VM1000 Series
‐113‐
6.4 Protocol Instruction
VM1000 series inverter communication protocol is an asynchronous serial
master-slave ModBus communication protocol. Only one device (the host) can build
a protocol (referred to as "Inquire / Command") in the network. Other devices
(slaves) can only respond to the host by providing the data "inquiry / command", or
make the appropriate action based on the host "inquiry / command." The host refers
to the personal computer (PC), industrial control equipment or programmable logic
controller (PLC) The slave means VM1000. Master can not only communicate with
a slave individually, but also broadcast information to the entire lower auxiliary. For
the master that access "inquiry / command" solely, slaves will feedback a message
(called a response). For broadcast information provided by master, slave needs not
feedback and response to the host.
6.5 Communication Frame Description
In RTU mode, information is sent with 3.5 character of interval of times at least. In diverse
character time of network baud rate, it is much easier to realize it. The first transmission
domain is the device address. The transmission characters that can be used is hexadecimal 0 ...
9, A ... F. Network devices monitor the network- bus constantly, including the pause at time
interval. When the first field (the address field) is received, each device decodes it and judges
whether it is sent to its own. After the last transmitted character, a times pause of 3.5 character
（at least） marks the end of the message. After this pause, a new message can begin.
The entire message frame must be used as a continuous flow of output. If it exceed times
pause of 1.5 characters, the receiving device will keep renewing the incomplete message and
assumes that the next byte is the address field of a new message. Likewise, if a new message
start within 3.5 character and continue in the previous information, the receiving device will
consider it as a continuation of the previous message. Because the final CRC field value is not
correct, this will cause an error.
RTU format is as follows:
START Time of 3.5 character
ADR Communication address：1~247
CMD
03 ： Read auxiliary parameters ； 06 ： Write auxiliary
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