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PICList Thread
'PIC versus AVR'
1997\12\23@081152 by Andrew Hall

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Hello all,

I'm starting a new project which requires a small embedded micro. At the
moment I am thinking of using the PIC or the Amtel AVR.

Does anybody have any opinions on which is the best generally ?

My initial impression is :

The PIC has excellent support and is popular but has a idiosyncratic
architecture?

The AVR is not so widely used but is generally faster (1 instruction per
clock at 16MHz) and is slightly more conventional in it's architecture
(although also Harvard).

These are just initial impressions, anybody care to comment ? Anybody
used both ?


TIA

--
Andrew Hall
Software Development Manager

Tectonic International Ltd.
MADE Enterprise Centre
Merthyr Industrial Estate
Dowlais
Merthyr Tydfil
CF48 2SR
Wales
United Kingdom

Tel +(44) (0)1685 722225
Fax +(44) (0)1685 722321

1997\12\23@094520 by John Payson

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> My initial impression is :
>
> The PIC has excellent support and is popular but has a idiosyncratic
> architecture?

The PIC is popular, since it works well, is cheap, can be programmed
with $5 worth of parts, and is practically indestructible (except if
you goof while programming it; the programming circuitry is touchy and
its <BLEEP> code-protect fuse can easily convert expensive window parts
into $20 tie pins.

As for its architecture, its description is more unusual than the arch-
itecture itself; the only "idiosyncracy" most programmers have to worry
about is the irksome way the memory is paged (once you get used to Mchip's
terminology).

> The AVR is not so widely used but is generally faster (1 instruction per
> clock at 16MHz) and is slightly more conventional in it's architecture
> (although also Harvard).

The AVR devices are faster, but their instruction set is not as well
suited to I/O as is the PIC's.  In particular, the PICs can access I/O
devices like any other register, whereas the AVR requires special in/out
instructions.  Beyond that, the PIC vs AVR debate is mainly one of taste;
the PIC allows easy access to all of its registers, but all operations
have to go through a single accumulator; the AVR has 32 general-purpose
registers (no dedicated accumulator) but access to anything outside those
registers is more difficult than with a PIC.

Six of one, 1/2doz of the other.

1997\12\23@145127 by Leon Heller

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In message <Jf4++spam_OUTAAsM7n0EwhzTakeThisOuTspamtect-uk.demon.co.uk>, Andrew Hall
<.....andyKILLspamspam@spam@TECT-UK.DEMON.CO.UK> writes
>Hello all,
>
>I'm starting a new project which requires a small embedded micro. At the
>moment I am thinking of using the PIC or the Amtel AVR.
>
>Does anybody have any opinions on which is the best generally ?
>
>My initial impression is :
>
>The PIC has excellent support and is popular but has a idiosyncratic
>architecture?
>
>The AVR is not so widely used but is generally faster (1 instruction per
>clock at 16MHz) and is slightly more conventional in it's architecture
>(although also Harvard).
>
>These are just initial impressions, anybody care to comment ? Anybody
>used both ?

I've used both the PIC 16C84 and the AVR 1200.

The AVR architecture is *much* easier to undertand than the PIC.

The AVR assembler doesn't have macros. This can easily be overcome by
the use of a general purpose macro-processor like m4.

Programmers for the AVR chips are a lot simpler than for the PICs,
needing virtually no hardware.

The AVR 1200 is cheaper in small quantities than the 16F84.

Leon
--
Leon Heller: leonspamKILLspamlfheller.demon.co.uk http://www.lfheller.demon.co.uk
Amateur Radio Callsign G1HSM    Tel: +44 (0) 118 947 1424
See http://www.lfheller.demon.co.uk/dds.htm for details of my AD9850
DDS system - schematic and software.

1997\12\23@203435 by Andrew Mayo

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A sufficiently powerful UV eraser *will* recover windowed parts - I
speak from experience. One used for water disinfection is ideal - watch
the ozone production, though. They are not particularly expensive and
will pay for themselves after a couple of boo-boos protecting JW
devices.

> ----------
> From:         John Payson[SMTP:.....supercatKILLspamspam.....MCS.NET]
> Reply To:     pic microcontroller discussion list
> Sent:         Wednesday, December 24, 1997 3:32 AM
> To:   EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU
> Subject:      Re: PIC versus AVR
>
[snip]

> The PIC is popular, since it works well, is cheap, can be programmed
> with $5 worth of parts, and is practically indestructible (except if
> you goof while programming it; the programming circuitry is touchy and
> its <BLEEP> code-protect fuse can easily convert expensive window
> parts
> into $20 tie pins.
>

1997\12\24@021612 by John Payson

picon face
> A sufficiently powerful UV eraser *will* recover windowed parts - I
> speak from experience. One used for water disinfection is ideal - watch
> the ozone production, though. They are not particularly expensive and
> will pay for themselves after a couple of boo-boos protecting JW
> devices.

Hmm... when I've tried baking protected parts for a weekend all I got was
parts that were 100% totally dead (the programmer couldn't even tell there
was a part in the socket since it just left RB7 floating always).

1997\12\24@185011 by Alex Holden

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> A sufficiently powerful UV eraser *will* recover windowed parts - I
> speak from experience. One used for water disinfection is ideal - watch
> the ozone production, though. They are not particularly expensive and
> will pay for themselves after a couple of boo-boos protecting JW
> devices.

I have an ordinary 8W eraser. Do you think it would recover a 16c74/JW
device if I left it in for long enough (I think I did try it for about two
hours before giving up and throwing it in a drawer).

> > The PIC is popular, since it works well, is cheap, can be programmed
> > with $5 worth of parts, and is practically indestructible (except if
> > you goof while programming it; the programming circuitry is touchy and
> > its <BLEEP> code-protect fuse can easily convert expensive window
> > parts
> > into $20 tie pins.
> >

-----------------------------------------------------------------------
: Alex Holden- Electronics student, Caver, and Land Rover enthusiast. :
:        http://www.geocities.com/CapeCanaveral/Lab/1532/             :
:            Linux- The choice of a GNU generation.                   :
-----------------------------------------------------------------------


'PIC versus AVR'
1998\01\04@174911 by Andrew Mayo
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I don't know - though I note the suggestion elsewhere to put a
magnifying glass over the top of the chip (hmm, does ordinary optical
glass actually bend UV light?).

The tube I use is I think 30W and about 9 inches long. It is a powerful
UV emitter used for water decontamination and someone gave it to me but
I think they can be purchased for around $50 or so - they are used also
as germicidal lamps - check your yellow pages.

Caveats

1. Make sure you shield it so you won't ever look at it - it is very
powerful and would probably not do your eyes a great deal of good.

2. Ensure you use such a tube in a well-ventilated area as the ozone
produced is quite substantial - this is, indeed, why these tubes are
used for their intended purpose.

That said, they sure do erase PICs very nicely. Ensure the chip is
securely mounted in conductive foam, of course. I have certainly erased
several code-protected 12C509 devices  - they erase in around 1 minute
under normal circumstances and take around 10 mins if code-protected.

{Quote hidden}

1998\01\04@180544 by Martin McCormick

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Andrew Mayo writes:
>I don't know - though I note the suggestion elsewhere to put a
>magnifying glass over the top of the chip (hmm, does ordinary optical
>glass actually bend UV light?).

No.  You need quartz glass.  Ordinary glass somewhat
blocks UV.

Martin McCormick

1998\01\04@180916 by Herbert Graf

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> -----Original Message-----
> From: pic microcontroller discussion list
> [KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU]On Behalf Of Andrew Mayo
> Sent: Sunday, January 04, 1998 17:48
> To: RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU
> Subject: Re: PIC versus AVR
>
>
> I don't know - though I note the suggestion elsewhere to put a
> magnifying glass over the top of the chip (hmm, does ordinary optical
> glass actually bend UV light?).

       Yes, although because UV is of shorter wavelength than visible light, th
e
focal point will I think be closer, therefore you have to adjust your focus
a little to ensure you cover
the whole piece of silicon. TTYL

1998\01\04@204819 by Joel A. Kunze

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My first post to this list and it has little to do with PICs
specifically :)

An ordinary magnifying glass will bend UV light quite well, problem is
that little to none of the UV light will make it through the lens. Of
course, the amount of UV that is transmitted is highly dependent on the
glass that is used in the lens. Also consider that a lot of the cheaper
magnifying glasses are made of plastic these days. Who knows, you might
get lucky and have a lens that will transmit enough of the 254nm light
to actually work better than no lens at all. I don't think a plastic
lens would last very long though.


Joel A. Kunze


Andrew Mayo wrote:
>
> I don't know - though I note the suggestion elsewhere to put a
> magnifying glass over the top of the chip (hmm, does ordinary optical
> glass actually bend UV light?).
>

snip

1998\01\04@230755 by Peter van Hoof

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This might actually not work all that great , ordinary glass absorbs many of
the frequency's present in the UV light-source  a reason why the windows on
these chips are made out of quartz glass

Peter

Check out how I think about Packard Bell computers
And tell me about your experience with them (I might put it on my page)
www.geocities.com/SiliconValley/Lab/5883
spamBeGonepvhspamBeGonespammicroserve.net

{Original Message removed}

1998\01\05@154751 by Matt Bonner

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Alex Holden wrote:

> I have an ordinary 8W eraser. Do you think it would recover a 16c74/JW
> device if I left it in for long enough (I think I did try it for about two
> hours before giving up and throwing it in a drawer).
>
Gawd, this thread again.  :-)

Mine is 14W.  I've erased _many_ protected 16C74 and 74A JWs without a
problem.  If programmed with a PICStart Plus, 1 to 2 hours is about
right.  If programmed with a ProMate II, it can take significantly
longer.

--Matt

1998\01\05@164515 by Herbert Graf

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> -----Original Message-----
> From: pic microcontroller discussion list
> [TakeThisOuTPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU]On Behalf Of Peter van Hoof
> Sent: Sunday, January 04, 1998 23:02
> To: RemoveMEPICLISTspamTakeThisOuTMITVMA.MIT.EDU
> Subject: Re: PIC versus AVR
>
>
> This might actually not work all that great , ordinary glass absorbs many
of
> the frequency's present in the UV light-source  a reason why the windows
on
> these chips are made out of quartz glass

       Ya, I didn't think about that fact until the message was already sent. T
TYL

1998\01\06@055442 by Harri Suomalainen

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On 5.1.1998, at 11:47, Andrew Mayo  wrote:
>The tube I use is I think 30W and about 9 inches long. It is a
powerful
>UV emitter used for water decontamination and someone gave it to me
but
>I think they can be purchased for around $50 or so - they are used
also
>as germicidal lamps - check your yellow pages.

There are other fast and *cheap* uv sourses available as well. I've
used eg. mercury vapor lamps (without
the outer glass envelope with fluorescents!!) with good success.
Output for the quartz-only mercury vapor
lamp will be mostly in the uv region (mostly 254, 366 and some 184nm
output peaks). Things like 125W
mercury vapor lamp (plain quartz) make *very* powerfull and very
cheap uv sources! Different ballasts
can be used to lower the output power if needed.

I think main output should be at 254nm peak with this method and
that's exactly what you want for
uv eraser. Soft uv like 366nm peak is no good for chip eraser. With
very powerfull exposure methods
you'll probably get very fast results but take care not to
over-exposure chips!

>Caveats
>
>1. Make sure you shield it so you won't ever look at it - it is very
>powerful and would probably not do your eyes a great deal of good.

That applies with those dirty cheap lamps very well too! 1-2min
exposure at few meters will make severe
burns all over you. I'd avoid all exposure!

>2. Ensure you use such a tube in a well-ventilated area as the ozone
>produced is quite substantial - this is, indeed, why these tubes are
>used for their intended purpose.

Yap, 254nm radiation will make ozon a lot. I think it's the radiation
that kills things when UV is used as
a sterilizing method.


--
Harri Suomalainen     habaEraseMEspam.....cc.hut.fi

We have phone numbers, why would we need IP-numbers? - a person in a
bus

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