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NEURN030000_220_A
NEURN030000_220_A
I-1-2 Protocol description
JI500 series inverter communication protocol is a asynchronous serial master-slave communication protocol, in the
network, only one equipment(Master) can build a protocol (known as “Inquiry/Command”). Other equipment(Slave) only
can response the “Inquiry/Command”of master by providing data or perform the corresponding action according to the
“Inquiry/Command”of master. Here, the master refers to a Personnel Computer(PC), an industrial control device or a
programmable logic controller (PLC), etc. and the slave refers to JI500 inverter. Master can communicate with individUal
slave, also send broadcasting information to all the lower slaves. For the single “Inquiry/Command”of master, slave will
return a signal(that is a response) to master; for the broadcasting information sent by master, slave does not need to
feedback a response to master.
Communication data structure JI500 series inverter’s Modbus protocol communication data format is as follows: in RTU
mode, messages are sent at a silent interval of at least 3.5 characters. There are diverse character intervals under network
baud rate, which is easiest implemented. The first field transmitted is the device address.
The allowable characters for transmitting are hexadecimal 0 ... 9, A ... F. The networked devices continuously monitor
network bus, including during the silent intervals. When the first field (the address field) is received, each device decodes it
to find out if it is sent to their own. Following the last transmitted character, a silent interval of at least 3.5 characters marks
the end of the message. A new message can begin after this silent interval.
The entire message frame must be transmitted as a continuous stream. If a silent interval of more than 1.5 characters
occurs before completion of the frame, the receiving device will 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 the interval of 3.5
characters following a previous message, the receiving device will consider it as a continuation of the previous message.
This will result in an error, because the value in the final CRC field is not right.
RTUframe format :
Frame header START
Time interval of 3.5characters
Slave address ADR
Communication address: 1 to 247
Command code CMD
03: Read slave parameters;06: write slave parameters
Data content DATA(N-1)
Data content: Address of function code parameter, numbers of
function code parameter, value of function code parameter, etc.
Data content DATA(N-2)
………………………
Data content DATA0
CRC CHK high-order
Detection Value: CRC value.
CRC CHK low-order
END
Time interval of 3.5characters
CMD (Command) and DATA (data word description)
Command code: 03H, reads N words (Max.12 words), for example: for the inverter with slave address 01, its start
address F0.02 continuously reads two values.
Master command information
ADR
01H
CMD
03H
Start address high-order
F0H
Start address low-order
02H
Number of registers high-order
00H
Number of registers low-order
02H
CRC CHK low-order
CRC CHK values are to be calculated
CRC CHK high-order
