C64 With Black Screen

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rmzalbar
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Re: C64 With Black Screen

Post by rmzalbar »

1541 VIA UC3
UC3_10.jpg
UC3_11.jpg
UC3_12.jpg



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Re: C64 With Black Screen

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UC3_14.jpg
UC3_17.jpg

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Re: C64 With Black Screen

Post by rmzalbar »

C64 CIA U2 with 1541 turned off
U2_off_5.jpg
U2_off_6.jpg
U2_off_7.jpg

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Re: C64 With Black Screen

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U2_off_8.jpg
U2_off_9.jpg

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Re: C64 With Black Screen

Post by C64Person »

Wow, this is incredible information! Thanks so much for doing this. I will try to start working through this, and will report what I find. Once again, no worries on the wait.

My knowledge of the oscilloscope is fairly limited beyond the basics. I understand active high and low, but I am not quite sure how to set rising/falling edge. Is changing the slope settings for trigger the same thing?
image.jpg

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Re: C64 With Black Screen

Post by rmzalbar »

Yes it is. That's the setting you can see in my images on the right Slope Rising or Slope Falling. Setting Slope Falling will prevent the trigger from firing when the signal is at rest above the trigger point on an active low signal, and will fire when it drops down to 0.

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Re: C64 With Black Screen

Post by C64Person »

Sounds good. I tried to run the command on the C64, but strangely it printed NOT PRESENT if I had the drive off, but the system just froze when I had the drive on; not even a READY prompt. Does this indicate anything?

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Re: C64 With Black Screen

Post by rmzalbar »

Certainly that's the wrong behavior.

The fact that it doesn't freeze and gives you a NOT PRESENT when the 1541 is off, means that it can at least think it's sent a command and didn't get a response. So something is working, on the c64 side. At least with the 1541 off, you should be able to compare the CIA pin signals against my "1541 off" captures to verify the CIA is generating all the signals you'd expect. Then if that looks OK, you could move onto the 1541 being on though that seems like it will be a bit more effort since it crashes each time and makes you retype the program.

Does pressing RUN/STOP break to a ready prompt when it freezes at least? That might save you some time. If not, you could try a stronger break by holding RUN/STOP and tapping RESTORE. You have to strike RESTORE quickly as it is designed to only respond to a quick strike. That's to keep it from resetting your program if you just casually press it by mistake.

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Re: C64 With Black Screen

Post by C64Person »

Pressing RUN/STOP doesn’t break to READY, but the RUN/STOP and RESTORE method does work.

I will compare the signals with the 1541 off to verify that the C64 is working properly, and then go from there.

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