Mouse interface card not working

Erik Hansen

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Aug 21, 2021, 6:01:33 AM8/21/21

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I do have an Apple II Mouse Interface card that seems not to work. It´s plugged into slot 4, but I think the firmware cannot be accessed as I only get random values for the mouse ID bytes (expected values should, as I understand it, be C405=$38, C407=$18, C40B=$01, C40C=$20, C4FB=$D6).
Is it possible to troubleshoot this problem, or is the card beyond repair?

Any help would be appreciated!

Br.
Erik

Michael J. Mahon

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Aug 22, 2021, 1:18:06 AM8/22/21

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It sounds like there may be a problem with the EPROM, which is easily
replaced.

The most straightforward approach to diagnosing the problem would be to
replace the EPROM with a known-good one and then test the card. (I presume
that the EPROM Is socketed.)

It would help others to diagnose the EPROM if you could dump its contents
and post them for examination, or you could compare them to a correct image
available on the web.

It is VERY improbable that anything more serious than a bad chip is wrong
with the card. ;-)

--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com

Erik Hansen

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Aug 22, 2021, 7:27:37 AM8/22/21

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On Sunday, August 22, 2021 at 7:18:06 AM UTC+2, Michael J. Mahon wrote:

Thanks for the advice Michael! It´s a bit of a learning ground to me, but I will order an EPROM reader/writer on ebay to proceed (TL866II seems like a decent option). I found the file “APPLE II ROMS/MOUSE - 342-0270 - C – 2716.bin”, which seems to be the correct file to compare with. And some schematics on the net indicated that the EPROM in question is Fujitsu MB8516 2k x8bit DIP24 (and yes it is scoketed). I will order a few of those too, and I will post an update when I have completed the testing. Thanks again!

Br,
Erik

Antoine Vignau

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Aug 22, 2021, 4:51:36 PM8/22/21

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Hi,
did you try the card in another slot? Let's say slot 2. Do you get the expected values there?
If so, the card would be OK, not the slot. On the contrary, the card would be not OK, and the slot, perhaps, OK!

Antoine

Michael J. Mahon

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Aug 22, 2021, 5:24:21 PM8/22/21

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You’re welcome, Eric.

BTW, you can read the EPROM using the Apple by writing a short machine
language program to select the slot, then copy $C800..$CFFF to RAM. The
copy should proceed from the lowest to the highest address, because
somewhere near $CFFF the card’s EPROM will be deselected, and the following
few bytes will be meaningless.

The region of RAM where the EPROM was copied can be BSAVEd to disk and
compared to the correct image. If the compare is equal (except for the
final few meaningless bytes) then the EPROM is good and doesn’t need to be
replaced.

The next most likely failure would be electrostatic discharge conducted
from the mouse inputs to the card to the chip(s) they connect to.

I am also assuming that the card was not electrically damaged by being
inserted or removed from a powered-on system.

Best of luck getting it working again.

Erik Hansen

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Aug 23, 2021, 1:41:38 PM8/23/21

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Thanks to both of you! Antoine, I have tried the card in multiple slots including some I have tested OK with other cards. Unfortunately no success. As for reading about using the bank switching of $C800..$CFFF to copy the EPROM, I have to say my memory from 35 years back is slowly returning :-) Seems like the best approach would be to do some refresh of my machine language skills and get the job done. I will keep you posted on the progress.

Br.
Erik