The max frequency for the 32-bit UDB up-counter is defined as 26MHz, look at the AC-specifications in the datasheet. You may use a clock with a lower frequency derived from IMO.
I am already using new clock resources with lower frequencies which derived from HFCLK. I have also tried KHz but If the IMO is higher than 24 MHz, I am getting warning.
My circuit is very simple, see below;
How is Pin_1 synchronized?
Best is usually to post your complete project, so we all can have a look at all of your settings. To do so, use
Creator->File->Create Workspace Bundle (minimal)
and attach the resulting file.
Found it: Set Pin_1 Synchronization to "Transparent".
Originally, I was using a Control Register to reset Counter. When I was change bit mode from 'Direct' to 'Sync (or Pulse)', problem is solved.