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PICList Thread
'On board programming + config bits query'
1997\05\29@084412 by Ian Cameron

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Hi,

I have just completed the prototype hardware and software for my
first PIC based project, but cannot seem to find the answer to a
couple of questions.

At the moment I am using the windowed CERDIP package of the PIC16C63,
but in the final product would like to use surface mount and serial
programming.  The number of boards is small (< 100), and although the
PICStart Plus programmer documentation does not recommend its use for
production I'm wondering if I can use it at all for serial
programming ?  Can I plug a header into the programmer and take the
five lines required to connections on my circuit ?  I have nothing
connected to RB7, and will probably need to use a jumper on RB6 for
programming.  /MCLR is pulled upto 5V via a 10k resistor, and the
rest of the circuit will not draw significant current during
programming.

Secondly, I tried programming a couple of the windowed 16C63 devices
with the configurations bits set to enable code protection.  Now
everytime I try to use them, they are not blank.  I thought these
devices were fully erasable, but it would seem I was wrong ? - Have I
now rendered these devices totally useless ?

Thanks for any help.

Cheers, Ian.

1997\05\30@042720 by STEENKAMP [M.ING E&E]

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Hi,

> Secondly, I tried programming a couple of the windowed 16C63 devices
> with the configurations bits set to enable code protection.  Now
> everytime I try to use them, they are not blank.  I thought these
> devices were fully erasable, but it would seem I was wrong ? - Have I
> now rendered these devices totally useless ?

Yep, Microchip covers the code protection fuse with some sort of mask to
block out UV.  I guess this is to prevent someone from taking a laser and
clearing only the CP fuse, thus unprotecting the PIC.  I do not know of
any way to erase that bit now.  (IMHO they should actually have omitted
the CP fuse in the JW devices since accidents do happen!  You only use
them for devlopment anyway.)

Niki
spam_OUTsteenkmpTakeThisOuTspamsun.firga.ac.za

1997\05\30@102150 by mike

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In message  <.....379487A3827KILLspamspam@spam@firga.sun.ac.za> PICLISTspamKILLspamMITVMA.MIT.EDU writes:
> Hi,
>
> > Secondly, I tried programming a couple of the windowed 16C63 devices
> > with the configurations bits set to enable code protection.  Now
> > everytime I try to use them, they are not blank.  I thought these
> > devices were fully erasable, but it would seem I was wrong ? - Have I
> > now rendered these devices totally useless ?
>
> Yep, Microchip covers the code protection fuse with some sort of mask to
> block out UV.  I guess this is to prevent someone from taking a laser and
> clearing only the CP fuse, thus unprotecting the PIC.  I do not know of
> any way to erase that bit now.  (IMHO they should actually have omitted
> the CP fuse in the JW devices since accidents do happen!  You only use
> them for devlopment anyway.)

Niki,

It is very reassuring to know that the same die is used in the JW
parts as in the OTP parts.

Having a different die (ie with the CP fuse) would be a Bad Idea.

Regards,

Mike Watson

1997\05\30@154841 by Ian Cameron

picon face
Hi,

> > Secondly, I tried programming a couple of the windowed 16C63 devices
> > with the configurations bits set to enable code protection.  Now
> > everytime I try to use them, they are not blank.  I thought these
> > devices were fully erasable, but it would seem I was wrong ? - Have I
> > now rendered these devices totally useless ?
>
> Yep, Microchip covers the code protection fuse with some sort of mask to
> block out UV.  I guess this is to prevent someone from taking a laser and
> clearing only the CP fuse, thus unprotecting the PIC.  I do not know of
> any way to erase that bit now.  (IMHO they should actually have omitted
> the CP fuse in the JW devices since accidents do happen!  You only use
> them for devlopment anyway.)

Thanks for the reply.  Sadly, I'm not having any luck getting rid of
the configuration bits, so it looks like these devices are now
useless :(  I wish Microchip had omitted the CP fuse as well !

Thanks.

Cheers, Ian.

1997\05\30@182345 by Andy Kunz

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face
>Thanks for the reply.  Sadly, I'm not having any luck getting rid of
>the configuration bits, so it looks like these devices are now
>useless :(  I wish Microchip had omitted the CP fuse as well !

Turn on your UV eraser and let them sit for several hours.

I blew the fuse and mine, and it erased after 2 hours of continuous
"suntan" with the quartz against the bulb.

Your mileage may vary.

If you insist on throwing them away, I have a trash can for them here at my
deskside - just mail them on over.

Andy

==================================================================
Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
         Hardware & Software for Industry & R/C Hobbies
       "Go fast, turn right, and keep the wet side down!"
==================================================================

1997\05\30@183954 by STEENKAMP [M.ING E&E]

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>
> It is very reassuring to know that the same die is used in the JW
> parts as in the OTP parts.
>
> Having a different die (ie with the CP fuse) would be a Bad Idea.
>
> Regards,
>
> Mike Watson

Hi,

I guess so - to ensure that development done on the JW will **ALWAYS**
work on the OTP device as well.
Just out of curiosity, would it be possible to erase a PIC with
something like X-Rays?

Niki
.....steenkmpKILLspamspam.....firga.sun.ac.za


'On board programming + config bits query'
1997\06\01@082736 by Paul B. Webster
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face
Andy Kunz wrote:
> If you insist on throwing them away, I have a trash can for them here
> at my deskside - just mail them on over.

 Might I too offer my services as the Australian equivalent "trash can"?
I have yet to try it, and need to experiment with exposure etc., but have
a fair idea I could recycle them if indeed the "fuzes" are all EPROM.

Niki Steenkamp:
> Just out of curiosity, would it be possible to erase a PIC with
> something like X-Rays?

 Ahh yes, that«s the question isn«t it?  OTP ones and all.  That said, I
should be surprised if what SHOULD be quite a brief and diffuse exposure
in an airport X-ray unit (presumably using an Image Intensifier) would
have such an effect.  I would expect the requirement to be more along the
lines of quite a few seconds close up to the tube.

 Typical continuous ("screening") currents of 1 to 2mA at 60KV represent
about 100W, so it is a bit more powerful than your UV tube.  Bursts of
about 200mA for a part of a second thus correspond to 10KW peak.  I have
no idea of the comparative conversion efficiencies in each case, nor the
effect of the different wavelengths.

 Some experiments are obviously in order.

 Paul B.

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