Subject:
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Re: LCD & serial connection
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 24 Apr 1997 12:56:04 GMT
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Original-From:
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Fred G. Martin <fredm@media^SayNoToSpam^.mit.edu>
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Viewed:
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2702 times
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It is possible you have a bum 6811. I have seen 6811's with bad
output address lines. this causes mirroring in the RAM as what should
be multiple locations get mapped to the same byte in memory. The
downloader thinks things are working because each byte appears to load
properly, but really things are broken.
Get a logic probe and look at the data, address, and select lines on
the RAM when the board is running. (Just turn it on and let it
execute garbage.) All of these pins should be oscillating rapidly.
If you see a pin that is open or stuck high or low, that's your
problem.
-Fred
> Thanks to those of you who sent your suggestions regarding the message
> below. I tried it all (replacing the LCD, checking each pin on both the
> RAM and the octal transparent latch 74HC373 for continuity, double
> checking the installed parts, I even replaced the memory chip) but after
> the pcode_hb.s19 file is downloaded, the board still won't beep and the
> LCD still does not display any messages. If there is anyone who has any
> other suggestions, I would appreciate it.
>
> Tunde
>
>
> Tunde Gyurics wrote:
> > I am still trying to get the PC-Handyboard connection to work. I got as
> > far as downloading the pcode_hb.s19 file successfully. After I turn the
> > main board power off and back on (reset), I should get a message on the
> > LCD screen ("Interactive-C v 2.81 9/28/93...") but instead the LCD screen
> > just stays lit on, without displaying any messages.
>
> and then Chuck McManis wrote:
> > Your LCD is bad. Either the logic to it is in error (check for
> > an open on the E pin) or the LCD itself is non-functional.
> > If IC cannot talk to the LCD it won't run.
>
> Not necessarily. There could be a problem with the memory circuit
> that is preventing pcode_hb.s19 from loading properly.
>
> Tunde, use a multimeter to check all of the connections in the memory
> circuit (including the 'hc373 chip). Make sure there are no adjacent
> shorts, and that all wires that should be connected are connected.
>
> -Fred
>
>
>
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Message is in Reply To:
 | | LCD & serial connection
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| Thanks to those of you who sent your suggestions regarding the message below. I tried it all (replacing the LCD, checking each pin on both the RAM and the octal transparent latch 74HC373 for continuity, double checking the installed parts, I even (...) (28 years ago, 24-Apr-97, to lugnet.robotics.handyboard)
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