9-13
9-4-4 Communication Protocol
(1) Serial communication specification
Table 9-4-3 Serial communication specification
Physical level Compliance with EIA RS-485 (2-wire type)
Number of connected
stations
Host x 1 unit, inverter x 31 units (Station address 1 to 31)
Transmission speed 19200, 9600, 4800, 2400, 1200[bit/s]
Synchronization method Start-stop
Transmission method Half duplex
Transmission protocol Polling/selecting, broadcast
Character type ASCII 7 bits
Character length Selection between 7 and 8 bits
Transmission distance Max. 500 m
Stop bit Selection between 1 and 2 bits
Frame length Standard frame: fixed to 16 bytes, short frame: 8 or 12 bytes
Parity Selection from none, even and odd
Error check method Checksum, parity, framing error
(2) Transmission protocol
It is the half duplex communication in the polling/selecting method. The inverter always waits for a
write request (selecting) or a read request (polling) from the host. The inverter, when receiving in the
wait state a request frame to the own station from the host, returns a response frame. Upon polling, it
returns data together. In the case of broadcasting (selection of all stations in a batch), no response is
returned.
Host
Inverter
Response interval time＋ (0～ 10ms)
10 msec or longer
・ Polling/selecting
・ Broadcast
No response frame
Host
Inverter
10 msec or longer
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