CCS/CC2652R: Connceted device automatic disconnection after 40 sec

Part Number:CC2652R

Tool/software: Code Composer Studio

While testing ProjectZero and SimplePeripheral projects I experienced, that the connection to the devices broken exactly after 40 sec period of time, like a timer.
After time passing by, a GAP_LINK_TERMINATED_EVENT message arrives, for an unknown reason.
I assume it should be some Gap settings, but I have no idea where to look for this.
The connection broke even, while different data reading, writting, enabled notify through the different services.
Is there any way to avoid this 40 sec connection „timer break” withe either in GAP settings or with any way reading and writing?

Many thanks for your help,

Laszlo