Master-slave principle, 31.10.2002 | Siemens RS-485 instruction

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
	CC1A7865.1en	HVAC Products
	31.10.2002	HVAC Products

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Siemens RS-485 manual Master-slave principle, 31.10.2002

Contents

31.10.2002 Master-slave principle Not Transmission mode RTUDevice address Reply by the slave Communication sequenceBaud rate 600 813 19.200 406 Time sequence Data query sequenceCommunication during the slave’s internal handling time Communication during the slave’s response time Slave address Fault handlingFunction code Data field CRC = SHR CRC Checksum CRC16Reply CRC16 = Following functions for the device will be available Writing 1 word Reading n words Writing n words Instruction Example Write switch-on threshold Hys1 = Word address =Reply Address Access Parameter Address Data Access Parameter Value range DefaultAddress tables REM TempRoff Setpoint Device 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

7865.1

Interface RS-485

RWF40...

Master-slave principle

Siemens Building Technologies

HVAC Products

31.10.2002