Siemens Industry Online Support
Siemens AG
Entry type: FAQ, Entry ID: 17398401, Entry date: 02/03/2004

Set-up restrictions when using universal modules

  • Entry
  • Associated product(s)

Does the size of the I/O address area have an influence on the size of the configuration byte?

If you configure a DP/DP coupler with an I/O address area of up to 16 bytes, one configuration byte is required. However, if you increase the input or output address area to more than 16 bytes (see Fig. 1 - Using a universal module with an 18 byte I-address area), this entails two configuration bytes. If you increase the address area yet further, three configuration bytes are required from the 33rd byte.

Under normal circumstances, you, as the user, have no influence over the use of the configuration bytes that are described here. The configuration bytes do not restrict the specified I/O address area of the DP/DP coupler either. They only form an internal setup limit that needs to be watched during configuration.

Fig. 1: Configuring a universal module with 18-byte input address area

You can configure up to 16 modules in a DP/DP coupler and the sum of the configuration data must not exceed 16 bytes. Please pay watch out for this when using universal modules and address areas greater than 16 bytes.

Security information
In order to protect plants, systems, machines and networks against cyber threats, it is necessary to implement – and continuously maintain – a holistic, state-of-the-art industrial security concept. Siemens’ products and solutions constitute one element of such a concept. For more information about industrial security, please visit