User manual - ATR144- 31
9 Serial communication
9.1 Slave
ATR144-xxxxx-T is equipped with RS485 and can receive/
broadcast data via serial communication using MODBUS RTU
protocol. The device can only be configured as a Slave by
setting Enab. on parameter 149 Mb.SL.. This function enables
the control of multiple controllers connected to a supervisory
system / SCADA.
Each controller responds to a Master query only if the query
contains the same address as parameter 150 sL. a d .(“Slave
Address”).
The addresses permitted range from 1 to 254 and there must
not be controllers with the same address on the same line.
Address 255 can be used by the Master to communicate with
all the connected equipment (broadcast mode), while with
0 all the devices receive the command, but no response is
expected.
The baud rate is selected on parameter 151 SL.b.r.(“Slave Baud
Rate”). The serial format is set on parameter 152 s . S . p . F. (“Slave
Serial Port Format”)
ATR144 can introduce a delay (in milliseconds) of the response
to the master request. This delay must be set on parameter
153 se. d e. (“Serial Delay”).
Each parameter modification is saved by the controller in
the EEPROM memory (100000 writing cycles), while the
setpoints are saved with a delay of 10 seconds after the last
modification.
Changes made to words that are different from those
reported in the following table can lead to malfunction.
Modbus RTU protocol features
Baud-rate
Selectable on parameter 151 SL.b.r.
1200bit/s 28800bit/s
2400bit/s 38400bit/s
4800bit/s 57600bit/s
9600bit/s 115200bit/s
19200bit/s
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