Presently I am having XBEE S2C module, previously I was using XBEE S2B module. With both the modules I was facing the same problem. Whenever I change the Pan ID of the XBEE module i need to update its firmware. Without updating the firmware the END DEVICE never gets associated with the COORDINATOR. For example: IF initially I have set the pan id of a XBEE module as A1 which has been associated to the coordinator having same pan id A1. Later if I am changing the pan id of the coordinator to A2 it takes the any network address easily on refreshing. But if I am changing the Pan id of end device to A2 it doesn't get associated to the coordinator on refresh. I have to update the end device XBEE xhip for it to get associate with the coordinator. Kindly let me know is this the thing I have to do always or anywhere I have to do some settings or follow some procedure to avoid everytime updation as it is time consuming.