> With the JW part - I've seen reports that not covering the window can
cause
> problems.

Yes, I want to second that.  When I was first learning about PICs, I tried
to do something quick and dirty with a 16C77 UV windowed part.  It would
sometimes work, and sometimes not.  I traced it down to the oscillator not
always running right.  After a while I noticed that it worked right only
when I had my hand within about 10cm of it.  While I was doing a mental
"what the ..." trying to understand how this minute change in capacitance
could possibly make a difference, someone else walked over about a meter
away and it worked fine whether my hand was there or not.  It turns out he
and my hand were blocking just enough of the light coming in from a nearby
window.  The oscillator didn't work unless the chip was kept sufficiently
dark.  Normal indoor room illumination was dark enough, but light from an
overcast sky was too bright.  I've religiously put stickers of the UV
windows of programmed parts ever since then.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olin@cognivis.com, http://www.cognivis.com

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