Jan-Erik Soderholm wrote:
> Rob Hamerling wrote :
>=20
>>I have set RA5/MCRL to digital I/O...
>=20
> OK, so the PIC "runs" as soon as Vdd is applied.
>=20
> The Prog Spec says :
>=20
> "Note:=20
> The Osc must not have 72 osc clocks while the device MCLR is between=20
> VIL and VIHH."
>=20
> And also :
>=20
> "Note: The MCLR pin should be raised from
> below VIL to above the minimum VIHH
> (VPP), within 250 =B5s of VDD rise."
>=20
> (Or simply appying Vdd *after* Vpp.)

I was aware of this possible issue, therefore I mentioned it explicitly.=20
But I read the datasheet differently, and the F88 datasheet doesn't=20
contain a diagram like figure 2.2 of the 12F627/etc datasheet, which is=20
very clear at this point.
BTW I don't understand how you can have 72 osc cycles before Vdd is appli=
ed.

Anyway I re-programmed the same F88 at least 20 times before, in the=20
same setup without plugging/unplugging anything except power and without=20
the Wisp628 dongle. And then suddenly without any (for me) apparent=20
reason it behaves differently.


> I thought that enabling internal-
> MCLR
> on *any* PIC also implied this requriment
> in timing between Vpp=20
> and Vdd.

I thought it was not needed for the F88.

> Not that the dongle must be able=20
> to *fast* short Vdd to GND and also fast release Vdd again.
>=20
> So you can't have to many uF's on the breadboard.
>=20
> A "few" uF's usualy works for me.

I have no uF's at all, only 1 100nF.

> You can't power the curcuit with something that
> can't be shortet to GND. A 7805 or 78L05 i usualy OK.

That's what I use.

> What you see is exectly this, you can't get the device
> into programming mode, and the Wisp628 can't "see" it at=20
> all.

>=20
> So, try the dongle again. Be carefull with your caps
> on the > breadoard.

I just tried to re-animate the seemingly dead F88. First without dongle:=20
no sign of life. So the suggestion of Stef Mientki didn't help!
Then I applied the dongle and now it does respond again and I could=20
reprogram it!   I tried it last night in the same way, but maybe the=20
working of the dongle isn't that consistent/reliable.
Now I can reprogram the F88 again even without dongle!!
However I don't have a comfortable feeling about it....

Regards, Rob.

--=20
Rob Hamerling, Vianen, NL phone +31-347-322822
homepage: http://www.robh.nl/
--=20
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