Hi
After modified the value of MOD then click "Write" buttom, will not the period change?

PDBx_MOD[MOD] specifies the period of the counter. When the counter reaches this value, it will be reset back to zero. If the PDB is in Continuous mode, the count begins anew. Reading this field returns the value of the internal
register that is effective for the current cycle of PDB.

The setting of LDMOD and LDOK in PDBx_SC will impact when the MOD will update.

Would you please tell us which example are you testing? Example in MQX or Kinetis SDK.
Which IDE are you using? CodeWarrior10.x or Kinetis Design Studio.
Best Regards,
Robin