When you say "massively" are we talking 1.2v or 3v or what? Knowing where the cut-off is does allow you to do one version for (S)GC and one for everything else, and in the (S)GC case maybe use a pull down resistor with an old buffer IC?
I have had some temperamental behavior from my loaner SCG, but it has a memory issue anyway. Dave On Mon, Oct 21, 2013 at 3:27 AM, Peter <[email protected]> wrote: > Hi, > > after spending a weekend looking why my SuperGoldCard system does not work > reliably with QL-SD, here is a quick result: > > Sometimes the ROMOE signal massively exceeds the maximum TTL low voltage > of 0.8V while in logic low state. This happens for about tens of > nanoseconds. > > The 30 year old circuitry of the QL was too slow to see this, so the fault > did not have immediate effects. But the QL-SD had to use a contemporary > PLD, with over 300 MHz maximum operating frequency, which considers it a > valid ROMOE signal and can malfunction. (Other signals than ROMOE may also > be affected.) > > I have also measured with a GoldCard, where a similar effect can be seen, > but it exceeeds the maximum TTL low voltage by a smaller amount. > > Conclusion One: There will be no easy way to make QL-SD work reliably with > the SuperGoldCard. The GoldCard appears to work with QL-SD, but is not > save in theory. > > Conclusion Two: Hardware designs for a (Super)GoldCard QL better use > slower/older circuitry. The other option: Don't expect valid signals, but > implement filters or other means, so the faulty signals do not cause > malfunction. > > Time allowing, I'll post oscilloscope pictures at the QL forum. It is > possible that other setups, particularly with Aurora and/or better power > supply, give better results. > > Peter > > _______________________________________________ > QL-Users Mailing List > http://www.q-v-d.demon.co.uk/smsqe.htm > -- Dave Park Sandy Electronics, LLC [email protected] _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
