Upon transition of the SIMATIC CPU's operating mode from STOP to RUN, the counter modules FM350 (6ES7350-1AH03-0AE0, 6ES7350-2AH00-0AE0) and  FM450 (6ES7450-1AP00-0AE0) are reinitialized and this sets the counter to zero.

In the case of counter modules FM350-1 (6ES7350-1AH03-0AE0), it is also possible to have "Count on in STOP" and "Retain counter value upon transition from STOP to RUN". For this you must parameterize the module as follows:

• Response to CPU STOP: continue processing
• Response to new parameters: reset only if parameters are changed

Counter module FM350-2 (6ES7350-2AH00-0AE0) can be parameterized so that the function of the internal module outputs Q0 to Q7 are also retained when the CPU is in STOP mode. For this you must parameterize the module as follows:

• Response to CPU STOP: continue processing

If the CPU switches to RUN mode however, the counter is set to zero. If the counter value is to be retained, it must be stored before the CPU is switched off or put into STOP mode, and reloaded upon restart of the CPU. Note here that the stored counter value might deviate from the actual plant situation. This is the case, for example, when an incremental encoder of a travel path is moved when the plant is without power.

The following parameters are sufficient from version 6ES7 350-2AH01-0AE0 onwards:

• Response to CPU STOP: continue processing

Here, the module can also continue counting over a STOP to RUN transition of the CPU if the module parameters / hardware configuration are not reloaded into the module.

Note
If an FM350-2 (6ES7350-2AH00-0AE0) is configured in HW Config and an FM350-2 (6ES7350-2AH01-0AE0) is slotted, the module behaves like an FM350-2 (6ES7350-2AH00-0AE0).