SDK11 S130 BLE Disconnect

HI:

      I Select the SDK11 as my BLE master.  

                           " nRF5_SDK_11.0.0_89a8197 \ examples \ ble_central \ ble_app_multilink_central \ pca10028 \ s130\arm5_no_packs ".

     I Select the Test board as my BLE master:   PCA10028 v1.2.0      2016.15     681374555

     softdevice: S130

      my probem:   

               My BLE master  can  connect with my ble slave ; this is OK.

               But, when My BLE Slave power cut off;  or restart,  the BLE Master will restart, too.    why???

 

thank you!