----- Original Message -----=20
From: "Dave Johnson" <dogrocket@MINDSPRING.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, August 13, 2001 4:43 PM
Subject: [PIC]: Trouble programming 16LF871 in circuit

I had a similar problem with to programming
device 16F870 with a JDM programmer
and it works then I connected chassiground from
 PC to the programmer!
Give it a try!
Regards
=C5keN

> I'm trying to program a PIC16LF871 in circuit and can't seem to get
> it to work no matter what I try. It always fails, sometimes on
> verify, sometimes it says the config bits weren't programmed, etc.
> Trying to program just the config bits (or just part of memory) it
> always tells me that the chip is code protected.
>=20
> I have programmed 16F877's in the same circuit without trouble
> (though that was a year ago - this project is recently unshelved).
> Does anyone have a clue why one should give me trouble and the other
> wouldn't? Any suggestions on what I might try?
>=20
> Here's a bunch more detail about what's going on and what I've tried:
>=20
> Setup
> -----
>=20
> I'm using a PicStart+ with a short homemade cable, MPLAB running
> under Win98 under VirtualPC on a Mac. On the board, I have the usual
> 5 lines (MCLR, Vdd, Vss, RB6, RB7) completely isolated from the rest
> of the circuit (shorting jumpers hook them up again when I want to
> run). This scheme has worked for me with no trouble before, on a
> couple different boards, with 16F84, 16F877, 16C774.
>=20
> Things I've tried:
> ------------------
>=20
> When I first had trouble and went poking around, I found Microchip's
> note about RB3 and LVP (and then read much of the voluminous
> discussion about it in the PICList archives :-). I assumed that was
> my problem, so I temporarily tied RB3 to Vss on the board though 10K,
> just for programming. It didn't seem to change anything.
>=20
> I was distressed to discover that the MPLAB/PicStart+ combo doesn't
> let you know if there's no PIC in the programmer (?!?!). And if there
> isn't, then the symptoms are just like what I'm seeing. This of
> course made me think that I just had a connection problem, but I
> double checked my connections all the way from the programmer to the
> PIC pins, and everything seems fine.
>=20
> I upgraded the PicStart+ firmware from 2.01 to 2.30, just in case.
> (getting desperate now...almost ready to try burning candles and
> chanting...)
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> What now?
> ---------
>=20
> I'm honestly not sure what to try next, which is why I'm writing here.
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> One thought I had: I'm only connecting one set of Vdd/Vss pins to the
> programmer, the others are still connected to the circuit. Maybe I
> should isolate the others, too? Didn't seem to matter on the 16F877,
> but I'm getting desperate.
>=20
> The boss is willing to spring for a Promate II and ICSP socket, if
> that will make a difference, but I'm not sure why a little extra
> drive capability would help.
>=20
> Anybody have any other ideas that I should try? Any thoughts on this
> are MUCH appreciated.
>=20
> Dave Johnson
>=20
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>=20
>=20

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