Thierry Godefroy wrote: > > > A phase locked loop with a programmable counter would do... > > > > That won't work well. The only signals permanently available for PLL input > > are the QL sync signals and they are not stable enough to generate a > > decent pixel clock to feed TFT monitors. > > I'd use a separate time base for output, and decouple input and output > > via screen RAM. > > I was speaking about the pixel sampling rate, for the input. Converters > using the same clock as for the output pixel clock fail to sample the > QL video signal, since there is no integer divisor common with 512 and > 640 (or 800), and even with a 1024 pixels/line clock rate, the blanking > times are not the same (meaning the apparent 2 divisor is in fact not > the right one). >
I don't need an integer divisor, just some extra precision for an adder ;-) (To determine the next input sampling point in the output clock domain.) BTW your PLL approach requires two asynchronous clock domains accessing the same RAM. This adds trouble, even if the RAM is dual ported. Not only in the digital part, but also to avoid noise from the input clock in the output signal. > Of course, to generate the (S)VGA signal, you'd need a perfectly stable > and independent clock. A dual port RAM would probably be needed as well. > For the QL, since there are only 8 colours, no A/D neither D/A are needed > (but they would be needed of the Q40/Q60). > That's why the difference is much more than just changing parameters. > Yes, but if the hardware can do the Q40, it can do the QL, as long > as the parameters required to rebuild the pixel clock can be adjusted > Yes, but if a video converter hardware can do the Q40/Q60, it is so much work that I could almost design a whole new mainboard. > (thus why a microcontroler would be a good idea). > Maybe. Depends on how non-volatile memory needs to be accessed. > > > to standard SVGA (I still could not find a modern LCD monitor that > > could properly display the 1024x512 screen of a Q60... > > > > I think you can give up that search :-( > > It only works with a modified video chip, and that only for a minority > > of monitors. > > If you know any such monitor, please let us know. > I still have one in the loft, but it's only an old 15" TFT. I think I published the model, but that won't help much if its not available. Peter _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
