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'[PIC] antistatic protection for PIC burner'
2008\07\09@141048 by Artie Jones

picon face
Hi all,

I just bought a programmer from Microchip and I ordered a ZIF socket (28 pin
SOIC) from Digikey. Now, I have to figure out how to provide static
protection for the homebrewed socket.

The programmer only uses a few pins, basically the other 24 pins
(PIC18F2550) will be floating, and thus it's possible to zap the chip when
inserting it into the socket for programming.

Rather then solder in large value resistors between each pin and VCC or
Ground, would it be possible to lay the socket over a piece of conductive
black foam?? I think the high resistance of the foam will not interfere with
the programming and it should connect every pin with every other pin, thus
providing protection against static.

Is this a viable solution???

Regards,

Art


PS:I still have large quantities of low profile SMT microprocessor crystals
for sale, 20 MHz, 16 MHz and 32.768 KHz. Email me direct for prices, paypal
accepted.

2008\07\09@143426 by Wouter van Ooijen

face picon face
> Rather then solder in large value resistors between each pin and VCC or
> Ground, would it be possible to lay the socket over a piece of conductive
> black foam?? I think the high resistance of the foam will not interfere with
> the programming and it should connect every pin with every other pin, thus
> providing protection against static.
>
> Is this a viable solution???

Don't bother with the programmer, anti-static yourself, your table, the
floor, etc. Or will you leave the chip in the progger forever?

--

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu

2008\07\09@144612 by olin piclist

face picon face
Artie Jones wrote:
> The programmer only uses a few pins, basically the other 24 pins
> (PIC18F2550) will be floating,

On that part make sure that PGM is held low even though it is not connected
to the programmer.  I would just tie it to ground at the socket.  Also put a
100nF to 1uF ceramic bypass cap from Vdd to Vss right at the socket.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\10@012050 by Xiaofan Chen

face picon face
On Thu, Jul 10, 2008 at 2:48 AM, Olin Lathrop <spam_OUTolin_piclistTakeThisOuTspamembedinc.com> wrote:
> Artie Jones wrote:
>> The programmer only uses a few pins, basically the other 24 pins
>> (PIC18F2550) will be floating,
>
> On that part make sure that PGM is held low even though it is not connected
> to the programmer.  I would just tie it to ground at the socket.

I do not think this is applicable to PIC18F2550. I do not this with either
PICKit 2 and MPLAB ICD2.

> Also put a
> 100nF to 1uF ceramic bypass cap from Vdd to Vss right at the socket.

This can be important for PIC18F2550 and many other PICs.
http://forum.microchip.com/tm.aspx?m=270347&mpage=2 (post 25)

Xiaofan

2008\07\10@081651 by olin piclist

face picon face
Xiaofan Chen wrote:
>> On that part make sure that PGM is held low even though it is not
>> connected to the programmer.  I would just tie it to ground at the
>> socket.
>
> I do not think this is applicable to PIC18F2550. I do not this with
> either PICKit 2 and MPLAB ICD2.

The 18F2550 definitely has a PGM pin.  On some PICs, including some 18F,
programming may fail if PGM is raised at the wrong time and LVP is enabled.
Apparently, raising MCLR to the programming voltage doesn't always enter
programming mode correctly if PGM was active and previously raised.  I have
seen this problem, including on a 16F628 and I think a 18F252 (suspected but
couldn't prove it).  I don't know for sure that the 18F2550 is immune to
this problem, so I assume it's not.

Note that LVP is implicitly enabled by a bulk erase, which many programmers
will do before trying to write the HEX file data to the target.  This means
LVP is enabled during most of the programming operation, even if it is
disabled in your code.

You can get away with it much of the time, but I make sure PGM is held low
during programming.  The OP asked about wiring up a socket adapter for a
in-circuit programmer, so this is just a matter of a wire between PGM and
Vss.  It seems like a no-brainer to me to install the wire.  I have on all
my programming adapters.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\10@095412 by Xiaofan Chen

face picon face
On Thu, Jul 10, 2008 at 8:19 PM, Olin Lathrop <.....olin_piclistKILLspamspam@spam@embedinc.com> wrote:
> Note that LVP is implicitly enabled by a bulk erase, which many programmers
> will do before trying to write the HEX file data to the target.  This means
> LVP is enabled during most of the programming operation, even if it is
> disabled in your code.
>
> You can get away with it much of the time, but I make sure PGM is held low
> during programming.  The OP asked about wiring up a socket adapter for a
> in-circuit programmer, so this is just a matter of a wire between PGM and
> Vss.  It seems like a no-brainer to me to install the wire.  I have on all
> my programming adapters.

Yes I agree that this is a good practice if you do not want to enable
low voltage programming. And most programmers support only
high voltage programming. So this makes sense.

By the way, PICkit 2 supports low voltage row erase when
Vdd is below the minimum bulk erase voltage. So does
MPLAB ICD 2. This is different from low voltage programming
though. Not many programmers support this feature.

Xiaofan

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