9.1 Overview on RS-485 Communication
9-2
9.1.1 RS-485 common specifications
Table 9.1-1
Items Specifications
Protocol FGI-BUS Modbus RTU Loader commands
(supported only on the
standard version)
Compliance Fuji general-purpose
inverter protocol
Modicon Modbus
RTU-compliant
(only in RTU mode)
Special command
dedicated for the
inverter support
software (Not
disclosed)
No. of supporting
stations
Host device: 1
Inverters: Up to 31
Electrical
specifications
EIA RS-485
Connection to
RS-485
RJ-45 connector or terminal block
Synchronization Asynchronous start-stop system
Transmission mode Half-duplex
Transmission speed 2400, 4800, 9600, 19200 or 38400 bps
Max. transmission
cable length
500 m
No. of logical station
addresses available
1 to 31 1 to 247 1 to 255
Message frame
format
FGI-BUS Modbus RTU Loader commands
Frame
synchronization
SOH (Start Of Header)
character detection
Detection of no-data
transmission time for
3-byte period
Start of header character
detection
(start code 96
H
)
Frame length
Normal transmission:
16 bytes (fixed)
High-speed transmission:
8 or 12 bytes
Variable length Variable length
Max. transfer data
Write: 1 word
Read: 1 word
Write: 100 words
Read: 100 words
Write: 41 words
Read: 41 words
Messaging system Polling/Selecting/Broadcast Command message
Transmission
character format
ASCII Binary Binary
Character length
8 or 7 bits (selectable by
the function code)
8 bits (fixed) 8 bits (fixed)
Parity
Even, Odd, or None
(selectable by the function code)
Even (fixed)
Stop bit length
1 or 2 bits (selectable by
the function code)
No parity: 2 bits/1 bit
Even or Odd parity: 1 bit
Select by parity setting.
1 bit (fixed)
Error checking Sum-check CRC-16 Sum-check
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