I wonder if the 'WIDESCREEN_MODI' byte at the end is what controls the ability to do split screen mode while in Radio mode. I've seen a couple of retrofits of the Mk III where this functionality is lost, although split screen works fine with the map and directions, you can't get radio/CD and directions. With the MK IV turning the radio on and off at the right time while changing the firmware can cure the problem, but with the MK III this does not work.

@RichardP1

The Byte for the widescreen-Mode controls the abbility for radio-split (radio on the left screenhald and navigation/position on the right)

Roland