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19 - SERIAL COMMUNICATION
Serial communication RS485 and protocol MODBUS – RTU
enable the controller ATR121/141 to receive and exchange
data, allowing the connection of more units to a centralized
supervisory system. The device can be configured only as
Slave unit.
LT (line termination) resistors on RS485 line must be removed
to avoid anomalies.
Each controller will respond to a request only if it contains the
same address which is written on parameter
. The range
of admitted addresses is 1 – 254. Address 255 is used to
communicate with all the connected units (Broadcast modality).
Single units ATR121/141 on the same line cannot have the
same address. Selecting 0 all connected units receive request
but no answer is required. ATR121/141 may delay the answer
to request. This delay (expressed as milliseconds) must be
entered on parameter
After each parameters change, the controller stores the new
values on EEPROM memory ( 100000 writing). Modified
sepoint values are stored on EEPROM memory with 10
seconds delay.
** Any operation on words which are not listed in the table
below may cause anomalies or malfunction.
Baud-rate
Selectable by parameter
MD.1 = 300bit/s
MD.2 = 9600bit/s
MD.3 = 19200bit/s
MD.4 = 38400bit/s
Format 8, N, 1 (8bit, no parity, 1 stop)
Supported
functions
WORD READING (max 20 word) (0x03, 0x04)
SINGLE WORD WRITING (0x06)
MULTIPLE WORDS WRITING (0x10)
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