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'Do 16C559/JW's get tired?'
1998\06\19@150812 by John P. Leonard

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I've been using a couple of 16C559/JW's (windowed EPROM's) for prototyping
and it appears that after several write/erase cycles, the PIC's will no
longer start-up if Vcc is < 4.8V.  At the beginning of the day, they will
fire-up with Vcc=3.6 (they're rated to operate down to 2.5V); but a couple
hours and several write/erase cycles later and they won't start-up unless
I set Vcc to nearly 5V.

I observed this several days ago, also.  The configuration bits aren't
being changed.  Are Mulder & Scully still subscribed to the list?
Anybody else been down this weird path?

John

1998\06\19@151805 by Mike Keitz

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On Fri, 19 Jun 1998 15:06:16 -0400 "John P. Leonard" <spam_OUTleonardTakeThisOuTspamsvsu.edu>
writes:

> but a
>couple
>hours and several write/erase cycles later and they won't start-up
>unless
>I set Vcc to nearly 5V.

Try doubling your erase time, and make sure to keep the windows clean.
Incompletely erased chips won't work at low voltage.  The bits that are
supposed to be erased are more likely to read as programmed as the
voltage drops.


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1998\06\22@070235 by Caisson

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> Van: John P. Leonard <.....leonardKILLspamspam@spam@TARDIS.SVSU.EDU>
> Aan: PICLISTspamKILLspamMITVMA.MIT.EDU
> Onderwerp: Do 16C559/JW's get tired?
> Datum: vrijdag 19 juni 1998 21:06
>
> I've been using a couple of 16C559/JW's (windowed EPROM's) for
prototyping
> and it appears that after several write/erase cycles, the PIC's will no
> longer start-up if Vcc is < 4.8V.  At the beginning of the day, they will
> fire-up with Vcc=3.6 (they're rated to operate down to 2.5V); but a
couple
> hours and several write/erase cycles later and they won't start-up unless
> I set Vcc to nearly 5V.
>
> I observed this several days ago, also.  The configuration bits aren't
> being changed.  Are Mulder & Scully still subscribed to the list?
> Anybody else been down this weird path?
>
> John

Hello John,

I think your PIC suffers from the Memory-effect on the individual
EPROM-cells.
This means that "unknown logic level" voltage widens (A Zero-state is not
from 0.0 thru 0.7 volts, but only to 0.5 volts for example. The High-state
suffers the same problem).  Heat (dissipation of the PIC itself or
otherwise) will worsen those
problems, because resistance will get higher.

Solution : allways over-erase the pic.

If you have a professional programmer try to verify your PIC at a low
voltage.  It will probably fail ...

Greetz,
 Rudy Wieser

1998\06\23@021758 by Dr. Imre Bartfai

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Hi guys,

could you tell me what the 16C559 is? (EEPROM/RAM size, word size, pins,
etc.)
It is not in may catalogue...

Imre


On Mon, 22 Jun 1998, Caisson wrote:

{Quote hidden}

1998\06\24@032127 by Jim robertson

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At 08:07 23/06/98 +0200, you wrote:
>Hi guys,
>
>could you tell me what the 16C559 is? (EEPROM/RAM size, word size, pins,
>etc.)
>It is not in may catalogue...
>
>Imre

Mistyped 16C558 I'd say.  I think that is what is been taken for granted.

Jim

{Quote hidden}

1998\06\26@205125 by ashley

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I think I have experienced this with a PIC 16C74/JW but I never checked Vcc.

I erased and reprogrammed it about 100 times or so.

The eraser was excellent and I had erase times down to 10 mins.

Occassionally the PIC  would reprogramme but  wouldn't run reliably, (may be my
programming).

I found that every now and then a 45 -60 min erase was neccessary and good
practise.

On one occasion my ISP lead 5v VCC wire broke while i was downloading  and upon
blank check it showed the code protection had been enabled on the upper 3/4.
Panic, Panic, but a 60 min erase sorted it out.


ASH -UK-






on 24 Jun 98, pic microcontroller discussion list wrote...

{Quote hidden}

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