Byron Jeff wrote:
> I'm in the process of working through a USB serial port based code
> dumper
> for the the 16F193X/18F182X series of chips.

The 16F1826 specifically is on my list.  Maybe it will happen this weekend.
It took a while to get samples in, and I sortof forgot about it.

> 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".

I haven't read the programming spec yet, but that sounds a lot like the sam=
e
procedure as the 3.3V parts.  Those don't allow MCLR to be raised to a high
voltage, so clocking in the key is the only means to enter programming mode=
..
So far that has always workes as expected for me.  I did notice that the ke=
y
is not the same for all parts.

> The progspec specifies that the key needs to be clocked in LSB first.

Microchip's Programming Obfuscation Division regularly dreams up new and
incompatible programming schemes, but so far they have all been LSB first.
You never know what the talented engineers at POD will come up with next,
but MSB first would really surprise me.

> However despite all my efforts, I've had no luck in getting the key to
> unlock programming mode.

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.

> So I ask: has anyone developed code for LVP programming of these
> parts?

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 SOURCE =
>
PICPRG > PICPRG_OP.INS.ASPIC.  Several magic key reset algorithms are
implemented in there.


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