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
