Serial ports for in-field programming for GEM Graphical OS Color Chips

In-field programming can be done several ways. The pinout shows both a ProgU and CommU for programming an communication UARTs. The ProgU, by default, is meant for just this. As a separate UART line the in-field updater does not have to physically disconnect the controller board from the host, they can just flip a DIP switch and connect on a secondary port.

Another option is to use the USB for updates and the UART for Host communication, or vice-versa.

Finally, you can use the same UART for both host communication and in-field updates. This has two sub-options. Either they can physically unplug the device or they can use what is called pass-through programming, where they program their host which in turn programs the Amulet.