Siemens Industry Online Support
Siemens AG
Entry type: Product note Entry ID: 4132236, Entry date: 08/27/1996

IM 308B Interface Module for ET 200U - Product Information

  • Entry
  • Associated product(s)


Concerns the product with Catalog No.:                                      


6ES5 308-3UB11   IM 308 for S5-115U/135U/150U/155U                          




_Limitations of the load-voltage monitoring function:_                      


Description of the problem:                                                 


If the IM 308B is used in S5-135U, -150U/H or -155U/H PLCs and              

the load-voltage monitoring function is activated (jumper AB-EX             

in the power-supply unit of the central controller open), a STOP            

of the CPU can lead to a condition where the outputs of the                 

distributed I/Os are not reset.                                             


Preconditions for this response are:                                        

- Operation with load-voltage monitor.                                      

- Load-voltage monitor is triggered (load voltage failure, i.e.             

  BASP (output inhibit) is generated by the power supply).                  

- Change of operating mode of the CPU to STOP while the load-               

  voltage monitor is triggered (e.g. due to a fault, activation             

  of the STOP switch, etc.).                                                


_Functional limitation:_                                                    

The above PLCs may not be operated with load-voltage monitor if             

an IM 308B module is plugged in, i.e. jumper AB-EX of the power             

supply must be in place.                                                    


_Limitation of the program check function:_                                 


If the user program is tested with the program check function,              

outputs of the distributed I/Os will be set even though the CPU             

is outputting a BASP signal (concerns PLCs S5-115/135/150/155U).            


If you use this function, make very sure that the setting of the            

outputs causes no dangerous conditions (e.g. by switching the               

control voltage off).                                                       




Security information
In order to protect technical infrastructures, systems, machines and networks against cyber threats, it is necessary to implement – and continuously maintain – a holistic, state-of-the-art IT security concept. Siemens’ products and solutions constitute one element of such a concept. For more information about cyber security, please visit
Rate entry
no rating
Requests and feedback
What do you want to do?
Note: The feedback always relates to the current entry / product. Your message will be forwarded to our technical editors working in the Online Support. In a few days, you will receive a response if your feedback requires one. If we have no further questions, you will not hear from us.