26 ATR401 - User manual
10 Serial Communication
ATR401-22ABC-T is provided with RS485 and can receive / broadcast data via
MODBUS-RTU protocol. Device can be con gured only as Slave.
This function allows to control multiple controllers connected to a supervisory
system. Each instrument will answer to a Master query only if contains same
address as on parameter 93
Allowed addresses are from 1 to 254 and there should not be controllers with
the same address on the same line.
Address 255 can be used by the Master to communicate with all connected
equipments (broadcast mode), while with 0 all devices receive command, but
no answer is expected.
ATR401 can introduce an answer delay (in milliseconds) to Master request.
This delay has to be set on parameter 94
At each parameters modi cation, instrument stores values in EEPROM
memory (100000 writing cycles), while setpoints are stored with a delay of 10
seconds after last modi cation.
NB: Modi cations made to Words di erent from those described in the
following table can lead to instrument malfunction.
Modbus RTU protocol features
Baud-rate
Selectable on parameter 92
4800 bit/sec 9600bit/sec
19200bit/sec 28800bit/sec
38400bit/sec 57600bit/sec
115200bit/sec
Format 8, N, 1 (8 bit, no parity, 1 stop)
Supported
functions
WORD READING (max 20 word) (0x03, 0x04)
SINGLE WORD WRITING (0x06)
MULTIPLE WORDS WRITING (max 20 word) (0x10)
Looking at the table here below it is possible to nd all available addresses
and functions:
RO = Read Only R/W = Read / Write WO = Write Only
Modbus
address
Descrizione Read Write
Reset
value
0 Device type RO EEPROM
1 Software version RO EEPROM
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