cc2530 end device

This depends on polling rate and beacon request interval of your end device. End device would only know it loses connection with its parent when device cannot get polling ack or there is no ack from its parent when end device sends message. After this, device will change to orphan status and sends orphan notification to join new parent. If there is no one responses to orphan notification, device will start to send beacon requests to search new parent node.

Dear Yk Chen
can we set the beacon request interval time of the end device?
how many times end device sends orphan notification to join new parent?

Orphan notification only is sent one time in original channel. Beacon requests interval can be set by changing-DBEACON_REQUEST_DELAY=100 in f8wconfig.cfg.

Dear Yk Chen

Can we say that maximum  device join time of end device is sum of the beacon request time and polling time?

is end devices also generate the beacons periodically?

is neighbor table create in end device?

1. Except beacon request time and polling time, there is NWK retry time.
2. Yes
3. I think neighbor table only is created in ZC and ZR.

No, the max join time would be polling time+NWK retry time+beacon requests time.

Dear YK chen
what is the default value of the network retry time?

Dear Yk Chen
is poll failure retries are send based on polling time?

No, poll failure retry is not based on polling time. It will restart immediately when polling failed.

Dear YK Chen
How can we tell how much time taken to complete poll failure retries?
what is the next step after sending two times of poll failure retries?

I suggest you to use Ubiqua Packet Analyzer to check over the air message when device loses connection.