On Mon, Jan 03, 2011 at 04:59:32PM -0500, Olin Lathrop wrote:
> Byron Jeff wrote:
> > I think I need to triple check the key. My test harness requires
> > putting in the individual bits. So with 32 bits, even though I double
> > checked the string, being one bit off can cause it not to work.
>=20
> The key I used was 4D434850h clocked in LSB to MSB order, then one 0 bit
> following the key.

That's 'MCHP' in ASCII. In binary it should be:

000010100001001011000010101100100

I will test it again when I get a chance.

>=20
> > Last thing I need to do is triple check that MCLR cannot be disabled
> > in LVP mode. I believe I saw that in the data sheet.
>=20
> Right.  They have to do that to support the key program entry mode.  If M=
CLR
> wasn't active, then the device could be running with MCLR low.  When
> running, it shouldn't be looking for the key.  If you want to use MCLR as=
 a
> input pin, you have to disable the key entry mode and use normal Vpp prog=
ram
> mode entry.

I figured as much. So I may end up programming the parts in HVP mode
anyway. But I want to make sure I know how to do LVP too.

Thanks again.

BAJ
--=20
Byron A. Jeff
Department Chair: IT/CS/CNET
College of Information and Mathematical Sciences
Clayton State University
http://cims.clayton.edu/bjeff
--=20
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