Discussion:
AP64 and PGM=12.75v 27c16 EPROM
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Jorge
2017-07-04 11:43:18 UTC
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This card gives 21 volts at VPP pin 21, this EPROM I want to program says 12.75. Will I fry it with 21?

Thanks,
--
Jorge.
Michael J. Mahon
2017-07-04 16:29:10 UTC
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Post by Jorge
This card gives 21 volts at VPP pin 21, this EPROM I want to program says
12.75. Will I fry it with 21?
Thanks,
Yes.

You'll need either higher programming voltage EPROMs or a card modification
to provide the lower programming voltage.
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Jorge
2017-07-04 22:32:27 UTC
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Post by Michael J. Mahon
Post by Jorge
This card gives 21 volts at VPP pin 21, this EPROM I want to program says
12.75. Will I fry it with 21?
Thanks,
Yes.
You'll need either higher programming voltage EPROMs or a card modification
to provide the lower programming voltage.
I have injected 12.8v throught the on/off switch, looking at the schematics (appleii-box.de) that's the best way to do it. Unfortunately it does not work 100%, some bits in some bytes can't be flipped to zero, or perhaps that eprom is kaput, idk.
Michael J. Mahon
2017-07-05 07:20:38 UTC
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Post by Jorge
Post by Michael J. Mahon
Post by Jorge
This card gives 21 volts at VPP pin 21, this EPROM I want to program says
12.75. Will I fry it with 21?
Thanks,
Yes.
You'll need either higher programming voltage EPROMs or a card modification
to provide the lower programming voltage.
I have injected 12.8v throught the on/off switch, looking at the schematics
(appleii-box.de) that's the best way to do it. Unfortunately it does not
work 100%, some bits in some bytes can't be flipped to zero, or perhaps
that eprom is kaput, idk.
EPROMS have standard protocols for programming, and many newer programmers
take that as a starting point and improvise. ;-)

For example, the software may try n shots at programming, reading after
each try, until it sees the correct state. Then it may do another n cycles
just to be sure the bit is well and truly programmed (or maybe 5n).

This has the advantage of adapting to the characteristics of the EPROM
being programmed.

I doubt that any Apple programmers did that, but it's high time that better
firmware was written--to an EPROM, of course! ;-)
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
groink_hi
2017-07-04 22:04:26 UTC
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My understanding of how the AP-64 works is that the cycles between writes are hard-encoded in the software. So, even if you were to adjust the voltage via the trimming resistor to the correct Vpp, the overall programming might not be good as the cycles might also need to be adjusted. And unfortunately the software on the AP-64 doesn't allow for that.
Jorge
2017-07-04 22:27:21 UTC
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Post by groink_hi
My understanding of how the AP-64 works is that the cycles between writes are hard-encoded in the software. So, even if you were to adjust the voltage via the trimming resistor to the correct Vpp, the overall programming might not be good as the cycles might also need to be adjusted. And unfortunately the software on the AP-64 doesn't allow for that.
Yes it does... :-) tomorrow I'll post a picture to show you why I say that. Mine does pulses of 48ms which are a bit too short (2 ms too short).
Jorge
2017-07-06 21:23:32 UTC
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Post by Jorge
Post by groink_hi
My understanding of how the AP-64 works is that the cycles between writes are hard-encoded in the software. So, even if you were to adjust the voltage via the trimming resistor to the correct Vpp, the overall programming might not be good as the cycles might also need to be adjusted. And unfortunately the software on the AP-64 doesn't allow for that.
Yes it does... :-) tomorrow I'll post a picture to show you why I say that. Mine does pulses of 48ms which are a bit too short (2 ms too short).
Now my AP64 is not working any more... sheesh.

I put a ROM, read it and compare and it says compare error. It reads garbage. The problem it seems is the CD4040 ripple counter that drives the address pins. I've been peeking with the scope and it's not driving the address pins correctly (some have clean square waves some have something in-between 0 and 5 volts, more like an analog signal). So I've replaced it a few times with other known-good CD4040s and they all do the same... grrr. Then replaced the 6821 for a 6820 and still the same.

Now I'm at a loss with this card... Any ideas?

Thanks,
--
Jorge.
Michael J. Mahon
2017-07-07 19:05:59 UTC
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Post by Jorge
Post by Jorge
Post by groink_hi
My understanding of how the AP-64 works is that the cycles between
writes are hard-encoded in the software. So, even if you were to adjust
the voltage via the trimming resistor to the correct Vpp, the overall
programming might not be good as the cycles might also need to be
adjusted. And unfortunately the software on the AP-64 doesn't allow for that.
Yes it does... :-) tomorrow I'll post a picture to show you why I say
that. Mine does pulses of 48ms which are a bit too short (2 ms too short).
Now my AP64 is not working any more... sheesh.
I put a ROM, read it and compare and it says compare error. It reads
garbage. The problem it seems is the CD4040 ripple counter that drives
the address pins. I've been peeking with the scope and it's not driving
the address pins correctly (some have clean square waves some have
something in-between 0 and 5 volts, more like an analog signal). So I've
replaced it a few times with other known-good CD4040s and they all do the
same... grrr. Then replaced the 6821 for a 6820 and still the same.
Now I'm at a loss with this card... Any ideas?
Thanks,
How do the address lines look with no EPROM installed?

If they are OK, then there may be a problem with the EPROM you're using. If
they're bad, then *something* on the card is loading them.
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com
Jorge
2017-07-14 16:46:48 UTC
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Post by Michael J. Mahon
How do the address lines look with no EPROM installed?
If they are OK, then there may be a problem with the EPROM you're using. If
they're bad, then *something* on the card is loading them.
With no EPROM in the socket all the signals look fine, so I have pulled a known good 2716 and it reads and compares ok all the times. Saved a copy, erased it, and could program it again ok.

So I think I have a bunch of kaput 2716s, that's the problem, not the AP64.

Thanks!
--
Jorge.
David Schmenk
2017-07-14 17:45:13 UTC
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Post by Jorge
Post by Michael J. Mahon
How do the address lines look with no EPROM installed?
If they are OK, then there may be a problem with the EPROM you're using. If
they're bad, then *something* on the card is loading them.
With no EPROM in the socket all the signals look fine, so I have pulled a known good 2716 and it reads and compares ok all the times. Saved a copy, erased it, and could program it again ok.
So I think I have a bunch of kaput 2716s, that's the problem, not the AP64.
Thanks!
--
Jorge.
I've ben playing around with programming 2716s for use as an Apple ][ character generator using a MiniPro USB on a Raspberry Pi. I'm sure it struggles to generate the 25V to program it with and often get compare errors on the first programming. Programming it again with the same data usually passes the compare test, but plugging it in to the Apple ][ as a character generator produces a lovely sparkle effect all over the display. Additional programming passes reduces the character sparkle, so I just make 10 passes over each EPROM and a get a solid, clear display. So, maybe make a bunch of passes to see if that improves the readability when plugged in.

Dave...
Kevin Dady
2017-07-14 18:13:38 UTC
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Post by David Schmenk
Post by Jorge
Post by Michael J. Mahon
How do the address lines look with no EPROM installed?
If they are OK, then there may be a problem with the EPROM you're using. If
they're bad, then *something* on the card is loading them.
With no EPROM in the socket all the signals look fine, so I have pulled a known good 2716 and it reads and compares ok all the times. Saved a copy, erased it, and could program it again ok.
So I think I have a bunch of kaput 2716s, that's the problem, not the AP64.
Thanks!
--
Jorge.
I've ben playing around with programming 2716s for use as an Apple ][ character generator using a MiniPro USB on a Raspberry Pi. I'm sure it struggles to generate the 25V to program it with and often get compare errors on the first programming. Programming it again with the same data usually passes the compare test, but plugging it in to the Apple ][ as a character generator produces a lovely sparkle effect all over the display. Additional programming passes reduces the character sparkle, so I just make 10 passes over each EPROM and a get a solid, clear display. So, maybe make a bunch of passes to see if that improves the readability when plugged in.
Dave...
the mini pro requires quite a bit of current to do its thing over USB, on my desktop PC I have to use a port that has nothing else plugged into it, and is not being shared with other ports etc
James Davis
2017-07-14 19:22:02 UTC
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Hi Jorge and David,

I have an EPROM WRITER CARD AP64E (that plugs into an Apple II expansion slot) and a UV ERASER LIGHT BOX (which Program and Erase, respectively: 2716/2732/2764 chips) for sale. If either of you are interested, see: <https://groups.google.com/forum/#!topic/comp.sys.apple2.marketplace/sj2KiKimgOs>.

James Davis

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