Hi Adrian,
do you mind sharing the manual? My unit is a crt, but it would be interesting to have a look at it. How is the LCD-DU connected with the DMC? Regarding DSDL I suppose it might be something like A429 but with a higher clock frequency => higher data rate.
BTW. the VDO chip in your unit: In my DMC there are a plenty of VDO chips with VGAxx labeling and they do not process video data, instead I think that these might be ASICs for DSDL, maybe glue logic and other custom peripherals.
Simon