Q. What do the RL and UD signals on the display connector do?
Some active TFT displays allow you to flip the displayed image by changing the horizontal and/or vertical scan direction.
Examples include some Sharp and NEC active displays. The Sharp LQ64D343 used in Eurotch evaluation systems has both up/down(UD) and right/left(RL) inputs, allowing you to flip an image top-to-bottom or right-to-left. This is useful for mirror-image applications. The NEC NL6448 displays include a single input that rotates the display 180 degrees.
The PNL_RL and PNL_UD signals on standard Eurotech display connectors are simple pull-ups to the PNL_PWR voltage. They can be connected to ground using shunts (eg. JP2 and JP3 on the GCPlus and GMaster) or with on-board resistors (eg. GMaster, Bitsy and Bitsy Plus).
If your display cable and panel support it, placing a shunt across the pins of JP2 or JP3 (GC Plus and GMaster) will change the scan direction of your display.
If you're currently using software display rotation (eg. CE) to rotate the display 180 degrees, you might consider using hardware rotation. Using the hardware drivers can lighten the load on the processor, freeing more resources for your application.