Hi all, thanks for your response.
Here some comments from my side.
To Flex727: This is exactly the behaviour I have also noticed. Although, the MI21 does not really changes randomly. If you notice, it has a max value e.g 8, and decreases litle by litle till to reach a min value (5 less), and then returns again to its max value. So it look to me like an internal control of the RTC, which every time sees that it has lost 5/10 of a second, it adds 5/10. In fact, in my operational software, we had realy noticed this, just by watching on the clock. We were adjusting it, according to an external watch, and now and then we could see some differences .
To Ausman: Yes indeed on my operational software I am using also two conductive sensors, coupled on wheels, and connected to VFC on the plc, in order to measure the driven distance. As we are talking about regularity rallies, it's essential to compare theoretical distance (based on given average and time), with really driven distance.
The sample software I downloaded, was just to show the problem I noticed.
I will have a look on your post later today, If I understand well, you propose to create my own RTC, based on the SB??
Regards