When Homekit framework gives callback that Accessory is Unrechable?

When Homekit framework gives callback that Accessory is Unrechable?


The understanding is after 30 seconds, the BLE connection between accessory and mobile is broken. When mobile app tries to write some characteristic the connection is re-established. Which means there is difference between the BLE disconnect and accessory is undechable status. So, Want to understand when the accesory is unrechable callback is returned by Homekit framework.