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Slothie · 25th Jul 2021, 4:09 pm

I've connected up to the MK14, and nothing worked, the display just flickered even with the VDU disabled. I removed the buffer ICs and the PIC and the MK14 is working again and the 1.5k memory is there and working fine (I did wonder if I'd made an error with the memory mapping), so that is OK and the memory mapping of that is correct and the problem is with the PIC and/or buffers (since thats the only untested part of the design that is also the part I am most suspicious of).
I did think at first maybe the NENIN output from the PIC might be floating causing the buffers to switch spuriously but I've looked at the code and the pin is always an output - which is why of course Karen put the diode there in the first place.
I'm going to jumper the buffers and see if it all works as it should (maybe using Karen's original "slow mode" firmware if necessary, so I can get a baseline and see where things go from there. Its slightly possible that there is a problem with the PIC chip as it wasn't new, if so I think I have another 877 somewhere. If not I can always take the one from my PIC14 and reprogram that.

25th Jul 2021, 4:09 pm	#74
Slothie Octode Join Date: Apr 2018 Location: Newbury, Berkshire, UK. Posts: 1,287	Re: Ortonview PCB I've connected up to the MK14, and nothing worked, the display just flickered even with the VDU disabled. I removed the buffer ICs and the PIC and the MK14 is working again and the 1.5k memory is there and working fine (I did wonder if I'd made an error with the memory mapping), so that is OK and the memory mapping of that is correct and the problem is with the PIC and/or buffers (since thats the only untested part of the design that is also the part I am most suspicious of). I did think at first maybe the NENIN output from the PIC might be floating causing the buffers to switch spuriously but I've looked at the code and the pin is always an output - which is why of course Karen put the diode there in the first place. I'm going to jumper the buffers and see if it all works as it should (maybe using Karen's original "slow mode" firmware if necessary, so I can get a baseline and see where things go from there. Its slightly possible that there is a problem with the PIC chip as it wasn't new, if so I think I have another 877 somewhere. If not I can always take the one from my PIC14 and reprogram that.