Appendix MD280/MD280N User Manual
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MD280 series inverter communication protocol is a asynchronous serial
master-slave communication protocol, in the network, only one equipment,
and master can build a protocol, (Named as “Inquire/Command”).
Otherequipments, slave’s response “Inquire/Command” of master only by
providing the data or doing the action according to the master’s
“Inquiry/Command”. Here, master is Personnel Computer, Industrial
Machine or Programmable logical controller, and the slave is inverter.
Master not only visits some slave, but also sends the broadcast information
to all the slaves. For the single master “Inquiry/Command”, all of slaves will
return a signal that is a response; for the broadcast information provided by
master, slave needs not feedback a response to master machine.
5
Communication Data Structure
ModBus protocol communication data format of MD280 series of inverter is
shown as following:
˄In RTU mode, messages start with a interval of at least 3.5 character
times. The first field then transmitted is the device address.The allowable
characters transmitted for all fields are hexadecimal 0 ... 9, A ... F.
Networked devices monitor the network bus continuously, including during
the silent intervals. When the first field (the address field) is received, each
device decodes it to find out if it is the addressed device. Following the last
transmitted character, a similar interval of at least 3.5 character times
marks the end of the message. A new message can begin after this
interval˅
The entire message frame must be transmitted as a continuous stream. If a
silent interval of more than 1.5 character times occurs before completion of
the frame, the receiving device flushes the incomplete message and
assumes that the next byte will be the address field of a new message.
Similarly, if a new message begins earlier than 3.5-character times
following a previous message, the receiving device will consider it a
continuation of the previous message. This will set an error, as the value in
the final CRC field will not be valid for the combined messages. A typical
message frame is shown below.
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