The fun never stops with this Z2

[christopher.mallery]

On to the next problem the TU-ART in the thing.  So this setup works.  A is 20h and B is 50h, the priority cable is attached from the 16FDCs out pin to the TU-ARTs in pin.  This setup successfully provides tty2 and tty3 to Z80 Cromix.  With this working I assumed the TU-ART was fully working.  Well bad assumption.  In the process of getting a printer working I was hitting hangs and just weird behavior so I assumed something wasn't quite right with interrupts, so I decided to test them with the metronome program in the TU-ART manual (attached and I have the TUARTs switches set as specified for the program) and it does nothing, it either locks up completely with no bell or it executes and quits back to CDOS which is odd because there is an infinite loop in it.  I have swapped TMS5501s and even tried different FDC cards.  Another odd thing is after it the metronome project locks up the machine continues to be locked up even after a reset.  I have to either wait until the +/-16V lines die (they die VERY slowly on this machine) or pull the TUART in order to get the machine running again.  I am scratching my head.  I would think it providing tty2 and tty3 in Cromix would be a good indicator that interrupts are working, but I cannot explain the metronome program not working.

Any ideas?

Thanks,

Chris

[Chris LaFond]

Chris,

Did you solve this problem? Does the program run correctly in CDOS? Does your TUART have any modifications? I have two TUART cards. One with bodges and one without. I have found they both work but the one with bodges doesn't like doing XModem transfers.

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[Christopher Mallery]

I got a metronome working in cdos.  The problem existed between keyboard and chair (i.e. the bell (ASCII 7) was not enabled in my terminal emulator, lol).  Using the TU-ART diagnostic found in the github I have determined that one of my TU-ARTs seems to be fully functional while my 2nd one is having issues.  On the second board the interrupt diagnostic (which seems to iterate over A and B's timers) gets stuck on A's Timer 5.  I haven't read the code well enough to understand if that is it waiting for A's Timer 5 to fire or that is indication that A's Timer 5 fires when it shouldn't.  Also the second board's switch 10 is apparently Schrodinger's switch.  It is acting as if it's both on and off at the same time which manifests as TMS5501 B being addressable in 2 IO Port ranges.  So if you have it set to 0x80 the machine won't boot because it is also conflicting with the 4FDCs 0x00 and if you set it to like 0xA0 TMS B is addressable on 0x20 and 0xA0.  I am still scratching my head on that one.  Either way I still can't get Cromix to print to my printer, lol.

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[Mike Arnold]

Christopher, sounds like you are really having fun! Your comment on  Schrodinger's port addressing got me thinking. I am sure that you have twigged this already, but it seems to me that A7 is not being decoded. Maybe IC46-8 which could have a fused output or just a dirty chip leg around that gate. I am intrigued to know what you eventually find.

[Christopher Mallery]

I hadn't gotten around to probing it yet, but you just saved me a ton of time! :)  Pin 8 on IC46 was snapped off.  Replaced it and now the switch is working right.  Now I just need to figure out the interrupt problem.  I swapped TMS chips to see if that changed anything, but it's still hung up on Timer 5 on TMS A, so it doesn't seem like the TMS is the issue.

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[Christopher Mallery]

The interrupt problem really has me scratching my head.  It appears that TMS A's Timer 5 is firing constantly, so anything downstream in the interrupt chain never gets serviced (this includes its own TMS B).  There is no circuit specific to certain interrupts, so I am confused.  I have swapped the TMS with multiple different ones and all the same behavior.  I know Timer 5 shares an interrupt with the parallel port, so maybe I will start looking there.

[Christopher Mallery]

It was a bad IC, the LS08 on the far left side (not looking at the board and forget the IC #).  I had tested all the ICs relatively recently, but I guess things happen, lol.  So I have two fully functional TU-ART boards!  Now I can finally focus on finishing my IMI7710 hard drive emulator!

[Mike Stein]

Well done! Congratulations!

Another emulator? Looking forward to seeing it; will it also emulate the HD5 and HD20 or just the 7710?

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