When RL78/G1D is used with host MCU, host MCU needs to wait about 1sec+ after RL78/G1D reset release before sending the API to RL78/G1D.
This wait time is required due to the stabilization time of 32kHz crystal on RL78/G1D for slow clock.
FYI. The default setting for the wait time is set 1sec in the application layer source code. Actual execution of this wait time is done inside the stack.
In reply to Toshio:
Bluetooth® Low Energy Protocol Stack User's Manual