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Siemens  Standard application AHU  CE1P3977en_02 
Building Technologies  Communication  01.02.2010 
Parameter  Range  Function 
−  2 RU  ing 1 RU, 1snsr+RU or 2 RU, the interface to the 
room unit connection is enabled. 
Settings    Goes to page with all settings relevant to param-
eterizing room units. 
Inputs    Go to page with temperature inputs. 
Reset required !! 
−   
−  Execute 
As a matter of principle, the controller must be 
set after parameterization to assume the data. 
 
Unit > System overview > Communication > Modbus 
Parameter  Range  Function 
Communication  −  OK 
−  Alarm 
Status of Modbus communication. 
Internal   
 
−  Disable 
−  Master 
−  Slave 
Generally enables internal MODBUS and func-
tion of MODBUS over RS485: 
−  Internal interface is disabled. 
−  Internal RS485 interface is master. 
−  Internal RS485 interface is slave. 
Internal Slave address  0…247  Controller address on the RS485 bus. 
Internal settings     
RS485    Go to parameter page for RS485 MODBUS in-
terface. 
TCP/IP  −    Go to parameter page for TCP/IP settings. 
Module1 Modbus  −    Go to parameter page for MODBUS interface on 
module 1. 
Module1 Modbus  −    Go to parameter page for MODBUS interface on 
module 1. 
Module1 Modbus  −    −  Go to parameterization page for MODBUS 
interface on module 1. 
 
Unit > System overview > Communication > Modbus > RS485 
 
Parameter  Range  Function 
  −    −   
Baud rate  −  2400 
−  4800 
−  9600 
−  19200 
−  38400 
Transmission rate on bus. All participants must 
have the same setting. 
Parity  −  Even 
−  Odd 
−  None 
Parity. All participants must have the same set-
ting. 
Stop bit  −  One 
−  Two 
Number of stop bits. All participants must have 
the same setting. 
Delay time  0…2147483647 [ms]  Response telegram delay. 
 
 
Parameter  Range  Function 
Response timeout  0…2147483647 [ms]  Settings access time for master. 
The master must undertake read access within this 
period, otherwise an alarm is triggered (this func-
tion is not yet fully implemented). 
Termination   
−  Passive 
Internal bus connection for the basis controller: 
−  No bus terminating resistor. 
MODBUS configuration 
RS485 MODBUS 
parameterization  
Basis Document Siemens Climatix Control System
BDCX.100820.01GB
Page 120