IGS-NT Communication Guide
135
9.3.2 Modbus RTU
Direct connection:
Modbus communication via RS232 – single controller (page 130), Modbus communication
viaRS485 (page 130), Modbus communicationviaI-LB+ (page 131)
8 data bits
1 stop bit
no parity
Modem connection
8 data bits
1 stop bit
no parity
Communication speed:
9600/19200/38400/57600 bps
Transfer mode RTU
Function codes
3 (Read Multiple Registers)
6 (Write Single Register)
10 (Command)
16 (Write Multiple Registers)
The response to an incoming message depends on the communication speed. The delay is not shorter than
the time needed to send/receive 3 and ½ characters.
Note: The complete description of Modbus communication protocol can be found in
modbus.org/docs/PI_MBUS_300.pdf
and
rtaautomation.com/modbustcp/files/Open_ModbusTCP_Standard.pdf.
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