Some TFT display require LCD enable pin. This pins is PB3 which also is BMS. This pins effect the booting up of the processor and care should be taken when used.
Please see datasheet for more details Smart | Connected | Secure | Microchip Technology
The pin is shown in this document as well http://www.ghielectronics.com/downloads/ChipworkX/ChipworkX_Module_Broch_Pinout.pdf