The xEMi’s are blank and can be configured as EM or HID (not both at the same time), If you try to read the blank xEMi tag using your HID reader, nothing will register as its simply a blank RFID. The easiest method, unfortunately, it to clone it using an existing ProxCard II, which is what I did. This also gives the the card as a back up, in case i lose my hand, and more importantly for testing.
If you have a RFID writer then I suspect you already understand how to write a valid HID sequence.
btw: i just cloned my xEMi and tested it this morning against our HID system, all tests were successful.