6
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Individual Functions
RS-422A/485 comm
unications are configured using 1 master (PLC) and a maximum of 31 slaves. Serial com-
munications between master and slave are normally started by the master and the slaves respond.
The master performs serial communications with one slave at a time. Consequently, you must set the address
of each slave before, so that the master can perform serial communications using that address. Slaves receiv-
ing commands from the master perform the specified function and send a response to the master.
Fig 6.38 Example of Connections between PLC and Inverter
Communications Specifications
The RS-422A/485 communications specifications are shown in the following table.
Communications Connection Terminal
RS-422A/485 communications use the following terminals: S+, S-, R+ and R-. Set the terminating resistance
by turning ON pin 1 of switch S1 for the last Inverter only, as seen from the PLC.
Fig 6.39 Communications Connection Terminal
Item
Specifications
Interface
RS-422, RS-485
Communications Cycle
Asynchronous (Start-stop synchronization)
Communications Parameters
Baud rate:
Select from 1,200, 2,400, 4,800, 9,600 and 19,200 bps.
Data length:
8 bits fixed
Parity:
Select from even, odd or none.
Stop bits:
1 bit selected
Communications Protocol
RS-422A/485
Number of Connectable Units
31 units max.
SYSMAC-series PLC
Inverter
Inverter
Inverter
Terminating resistance (1/2W, 110 Ohms)
RS-422A
or RS-485
Switch
S1
O
F
F
1
2
Terminating
resistance
