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28 ATR 621 - User manual

9 Serial communication

ATR621-13ABC-T is provided with isolated RS485 serial and can receive/

transmit data via MODBUS RTU protocol. Device can be con gured as master

or slave.

Modbus RTU protocol features

Baud-rate

Selectable by parameter 78



 4800 bit/sec  9600bit/sec

 19200bit/sec  28800bit/sec

 57600bit/sec     115200bit/sec

Format

Selectable by parameter 79



   8 data bits, no parity, 1 stop bit.

   8 data bits, odd parity, 1 stop bit.

  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)

9.1 Slave

ATR621-13ABC-T can operate as slave unit setting    on parameter 77

 : this function allows to control multiple controllers connected to a

supervisory system. Each instrument will answer to a Master query only if

it contains same address as on parameter 80  . Allowed addresses are

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 devices without knowing their addresses (broadcast mode), whi-

le with address 0 all devices receive command, but no answer is expected.

ATR621 can introduce an answer delay (in milliseconds) to Master request.

This delay has to be set on parameter 81 . At each parameters modi

cation, instrument stores values in EEPROM memory (100000 writing cycles).

NB: Modi cations made to Words di erent from those described in the fol-

lowing table can lead to instrument malfunction.

Here below list of available addresses

RO = Read Only R/W = Read / Write WO = Write Only

Pixsys ATR 621 series User Manual

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