ATR 421 - User manual 29
 Pressing   red display visualizes Lo a d. Con rm with 
O
K
. Controller 
loads news values and restarts.
•  With the controller not connected to the power 
supply:
  The memory card is equipped with an internal 
battery with an autonomy of about 1000 uses.In-
sert the memory card and press the programming 
button. When writing the parameters, led turns red 
and on completing the procedure it turns to green. 
It is possible to repeat the procedure without any 
particular attention. 
Updating Memory Card
To update the memory card values, follow the procedure described 
in the  rst method, setting ---- on red display so as not to load the 
parameters on controller
3
. Enter con guration and change at least one 
parameter. Exit con guration. Changes are saved automatically.
9  Serial communication
ATR421-12ABC-T is provided with isolated RS485 serial and can receive/tran-
smit data via MODBUS RTU protocol. Device can be con gured as master or 
slave. 
Modbus RTU protocol features
Baud-rate
Selectable by parameter 78 
bd.rt.
4.8 k 4800 bit/sec  9.6 k 9600bit/sec
19.2k 19200bit/sec  28.8k 28800bit/sec
57.6k 57600bit/sec  11 5 . 2  11520 0 bit /sec
Format
Selectable by parameter 79 
se.p.s.
8. n .1  8 data bits, no parity, 1 stop bit.
8. o .1  8 data bits, odd parity, 1 stop bit.
8. e.1  8 data bits, even parity, 1 stop bit.
Supported 
functions
WORD READING (max 20 word) (0x03, 0x04)
SINGLE WORD WRITING (0x06)
MULTIPLE WORDS WRITING (max 20 word) (0x10)
3 
If at starting controller shows memo it means that no data are stored into the Memory Card, 
however values can be update.