On Sat, Jan 01, 2011 at 08:55:05AM -0500, Olin Lathrop wrote:
> Byron Jeff wrote:
> > I'm in the process of working through a USB serial port based code
> > dumper
> > for the the 16F193X/12F182X series of chips.
>=20
> The 16F1826 specifically is on my list.  Maybe it will happen this weeken=
d.
> It took a while to get samples in, and I sortof forgot about it.

That's good. It'll be good to see if you have any problems.

>=20
> > I'm interested in working with the new LVP setup that Microchip has
> > put on
> > the chip. The basic idea is to clock in a "programming key" while
> > MCLR is
> > held at Vil. The key is a 32 bit pattern that converts to ASCII as
> > "MCHP".

[Snippage]

> > However despite all my efforts, I've had no luck in getting the key to
> > unlock programming mode.
>=20
> Usually PGC and PGD have to be held just right while MCLR is blipped just
> right before the key can be clocked in.  Vdd might also require special
> handling.  Check the spec and make sure your code does that.

I've poured over the progspec. There doesn't seem to be anything special.
There's no requirement that MCLR be blipped at all, though I tested it
both ways. I start the process with PGC and PGD both at Vil. I tested
it both with blipping MCLR and not. Also while there is a minimum time
specified between MCLR's falling edge and the start of clocking the key
(of 250 uS), there is no maximum time specified.=20

So from everything that I've gathered so far, there should be no problem
with starting the part with MCLR, PGD, and PGC all at Vil, waiting an
arbitrary amount of time, then clocking in the key.

As I said in my original post, figures 8-9 and 8-10 of the progspec shows
the key clocked in with 33 clocks. But it's only a 32 bit key. So I'm
trying to figure out if I need to clock that extra clock or not (as the
text for LVP entry does not discuss the extra clock in the description).
I did test both with 32 clocks and 33 clocks, and got no joy with either.

>=20
> > So I ask: has anyone developed code for LVP programming of these
> > parts?
>=20
> Not for those parts just yet, but I have for other parts that use a magic
> key sequence to enter programming mode.  You can look at my code if you
> want.  Install the Development Software release from
> http://www.embedinc.com/picprg/sw.htm, then look around in the file SOURC=
E >
> PICPRG > PICPRG_OP.INS.ASPIC.  Several magic key reset algorithms are
> implemented in there.

Will do. Thanks for the pointer.

BAJ

>=20
>=20
> ********************************************************************
> Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
> (978) 742-9014.  Gold level PIC consultants since 2000.
> --=20
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist

--=20
Byron A. Jeff
Department Chair: IT/CS/CNET
College of Information and Mathematical Sciences
Clayton State University
http://cims.clayton.edu/bjeff
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.