Table of Contents
Advertisement
Quick Links
Master-slave principle
CC1A7865.1en
31.10.2002
Interface RS-485
The RS-485 interface is used for integrating RWF40... controllers into data networks
via MOD bus protocol.
Application examples:
Process visualization
-
Plant control
-
Reporting
-
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).
Siemens Building Technologies
HVAC Products
7
865.1
RWF40...
Advertisement
Table of Contents
Related Manuals for Siemens RS-485
Summary of Contents for Siemens RS-485
- Page 1 Interface RS-485 The RS-485 interface is used for integrating RWF40… controllers into data networks via MOD bus protocol. Application examples: 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.
- Page 2 Data word Parity bit 8 bit A maximum of 31 slaves can be addressed via the RS-422 / RS-485 interface. Data query / instructions delivered by the master to a slave via the re- spective device address. The addressed slave responds.
- Page 3 Identification of the data query or end of the reply with a data format of 10 / 9 bits. Waiting time = 3 characters * 1000 * x bits / Baud rate Siemens Building Technologies HVAC Products Data query by the master...
- Page 4 The master is not allowed to make any data queries during the slave’s response time. Data queries made during that period of time cause all data currently on the bus to become obsolete. 4/14 Siemens Building Technologies HVAC Products Data query Reply...
- Page 5 The function code is OR linked with 0 x 80, that is, the MSB (most significant bit) will be set to 1. Example Data query: Reply: Special cases In the following cases, the slave does not reply: Siemens Building Technologies HVAC Products Slave address Function code 1 byte 1 byte Device address of a certain slave...
- Page 6 The following functions for the device will be available: Function number 0x03 / 0x04 0x06 0x10 6/14 Siemens Building Technologies HVAC Products CRC = CRC XOR ByteOfMessage For (1 to 8) CRC = SHR (CRC) if (flag to the right = 1)
- Page 7 Word address = 0x000C Instruction: (write the first part of the value) Reply (like instruction): Instruction: (write the second part of the value) Reply (like instruction): Siemens Building Technologies HVAC Products Function 0x03 Address of the or 0x04 1 byte...
- Page 8 Following is a description of all process values (variables) with their addresses, data type and type of access. Where: R / O R / W float word The process values are subdivided into logic areas. 8/14 Siemens Building Technologies HVAC Products Slave Function Address 0x10 of first word 1 byte...
- Page 9 R / W 0x0044 float R / W 0x0046 float R / O 0x0048 float R / O Siemens Building Technologies HVAC Products Parameter Actual value E1 Actual value E2 Actual value E3 Current setpoint First setpoint SP2 (=dSP) Second setpoint...
- Page 10 R / W 0x050F float R / W 0 = local 1 = remote setpoint 2 = fully remote 10/14 Siemens Building Technologies HVAC Products Parameter Device data char SWVersion [11+1] Software version char VDNNr [13+1] VdN number Parameter...
- Page 11 Measured value range crossing input 3 Reserved 0x0201 word B15 B14 B13 B12 B11 B10 Reserved Interface present Analog output present Siemens Building Technologies HVAC Products Access R / O Outputs and states Output 1 off Output 3 off Output 2 off...
- Page 12 The remote parameters are stored in RAM and will no longer be available after a power failure. After «Power-up», the default values will be used. 12/14 Siemens Building Technologies HVAC Products Operating mode «LOCAL», «REMOTE SETPOINT» or «FULLY REMOTE» Setpoint remote...
- Page 13 K2 = energized, K3 = deenergized ® analog output = 10 V or 20 mA K2 = deenergized, K3 = energized ® analog output = 0 V or 0 / 4 mA Setting the «RY» by the management system has no impact. Siemens Building Technologies HVAC Products 13/14 CC1A7865.1en...
- Page 14 If supervision of the actual value is not desired, the switching hystereses in the RWF40... must be set to the respective maximum value. In operating mode «REMOTE SETPOINT», the control algorithm ensures this kind of supervision. ã2002 Siemens Building Technologies Subject to change! 14/14 Siemens Building Technologies HVAC Products CC1A7865.1en...