6.3. Bootloader I/O pin usage

The bootloader uses the following I/O pins of the microcontroller:

• D- and D+ are used to communicate with the USB host.
• RB6 is driven high to turn on the yellow LED, but never driven low.
• RB7 is driven high to turn on the green LED, but never driven low.

The bootloader does not use any other I/O pins.