My reward may have been too refreshing on Thursday as I was struck down with hungover stupidity on Friday...I spent a couple of hours of the sweltering afternoon wondering why I could write to, but not read from, the user VIA, which I thought I had working. I fiddled with timings and had a mess of scopes and logic analysers, simulation models and bits of paper with graphs on...then I found the problem...
...pretty stupid really. On the plus side it forced me to tidy up the multiplexer controller.
I soldered on a few more chips today and now have interrupts working from the user via and the extra buttons on the side can now be used to break into the debug by generating an NMI.
This evening, I soldered on a Flash EEPROM and ported a quick test program and the Flash EEPROM is being recognised.
I also have to shamefully share the awful mess I made adding a pull up to the irq line...I'm not usually awful at soldering and rework but this is a real dogs breakfast! More thought will be put into doing the econet interrupt and NMI pullups!
I've not dared clean off the horrible sticky flux properly yet - I'll leave the solder mask "glue" to cure in the sun tomorrow first.
In theory all the hardware that is needed to attach a proper keyboard is now in place but I will need to code up a special "part-6522, part latch" system VIA. Most of the hard work will have been done by Mike Stirling, Hoglet and I'll just break into a 6522 from the BeebFPGA project.
D
...pretty stupid really. On the plus side it forced me to tidy up the multiplexer controller.
I soldered on a few more chips today and now have interrupts working from the user via and the extra buttons on the side can now be used to break into the debug by generating an NMI.
This evening, I soldered on a Flash EEPROM and ported a quick test program and the Flash EEPROM is being recognised.
I also have to shamefully share the awful mess I made adding a pull up to the irq line...I'm not usually awful at soldering and rework but this is a real dogs breakfast! More thought will be put into doing the econet interrupt and NMI pullups!
I've not dared clean off the horrible sticky flux properly yet - I'll leave the solder mask "glue" to cure in the sun tomorrow first.
In theory all the hardware that is needed to attach a proper keyboard is now in place but I will need to code up a special "part-6522, part latch" system VIA. Most of the hard work will have been done by Mike Stirling, Hoglet and I'll just break into a 6522 from the BeebFPGA project.
D
Statistics: Posted by dominicbeesley — Sat Jun 21, 2025 11:35 pm