Siemens Industry Online Support
Siemens AG
Entry type: FAQ Entry ID: 217293, Entry date: 02/09/1998

Monitoring whether OP on STEP 7 is on-line or off-line

  • Entry
  • Associated product(s)

How can I see in my STEP 7 user program whether my OP is on-line or off-line?

Proceed as follows to evaluate the operating state of the OP in STEP 7:

  1. Create an interface area 32 bytes long in the STEP 7 in order to evaluate the life bit of your OP.
  2. Open the self-extracting file by clicking the following symbol:
    watchdog.exe (22738 Bytes)
  3. Copy the included function block into your STEP 7 configuration. To do this click with the right mouse button "Insert new object" => "1 External source" in the folder "Sources" (SIMATIC Manager => "SIMATIC Station" => "CPU" => "S7 Program" =>"Sources").
  4. Enter the number of the interface data block and the initial address into this function block. A standard value for the monitoring time is 10s.

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