Siemens RS-485 manual Master-slave principle, 31.10.2002

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7865.1

Interface RS-485

RWF40...

The RS-485 interface is used for integrating RWF40… controllers into data networks via MOD bus protocol.

Application examples:

-Process visualization

-Plant control

-Reporting

Master-slave principle

Communication between a PC (master) and a device (slave) via MOD bus is based on the master-slave principle in the form of data query / instruction – reply.

A master computer controls the exchange of data and can address up to 99 controllers via device addresses (slaves).

CC1A7865.1en

Siemens Building Technologies

HVAC Products

31.10.2002

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Contents 31.10.2002 Master-slave principleNot Transmission mode RTUDevice address Reply by the slave Communication sequenceBaud rate 600 813 19.200 406Time sequence Data query sequenceCommunication during the slave’s internal handling time Communication during the slave’s response timeSlave address Fault handlingFunction code Data fieldCRC = SHR CRC Checksum CRC16Reply CRC16 = Following functions for the device will be availableWriting 1 word Reading n wordsWriting n words Instruction Example Write switch-on threshold Hys1 = Word address =Reply AddressAccess Parameter Address Data Access Parameter Value range DefaultAddress tables REM TempRoff SetpointDevice state Address Data type Access Parameter«FULLY REMOTE» SPR Description of operating modesRemote RK1 Operating mode Control strategy for Dependent switchingFloating output with Modulating burner
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