12F629 woes

Started by jrem123 June 4, 2003
A while back I posted about problems programming some 12F6x's using
the Olimex PB2G (JDM style) programmer. Well, I think I have had an
awakining.

The problem is reprogramming them when their internal oscillator is
set to run. Someone mentioned that, so I'm not taking credit. As
soon as you plug them into the JDM they get VDD and VSS so they start
to run.

So I figured out how to reprogram these devices when that pesky
oscillator is running. Someone else mentioned (Wouter?) that the vpp
(mclr) has to be high prior to vdd (vcc). Well there isn't any way
to do this with the JDM programmer hardware . . . but wait. I put a
9v battery on VSS and MCLR, hit the program button, plugged in the
DB9 serial cable, unplugged the 9v battery, and if I'm really quick
it works! The battery holds MCLR high until the VSS comes up, just
as intended.

So, I guess my points are) if you have the JDM and want to do the
12F6x's, use an external oscillator, b) if you have to use the
internal oscillator you get one shot at it or you have to c) jump
though hoops to get them cleared, and d) either I'm a glutton for
punishment, bored, persistent as hell, or some of all three.

Regards, John Remington www.jrem.com




> The problem is reprogramming them when their internal oscillator is
> set to run. Someone mentioned that, so I'm not taking credit. As
> soon as you plug them into the JDM they get VDD and VSS so they start
> to run.

In my experience
- the Vpp before Vcc sequence is (only) needed when you use internal
/MCLR
- problems with the oscillator indicate that the rise time from 0 to Vpp
is too slow

Wouter van Ooijen

-- -------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products



where do you get the programming voltage specs and sequences? I
perused the mid-line reference catalog and the device data sheets, and
I don't see where the specs are listed . . . thanks.
--- Wouter van Ooijen <> wrote:
> > The problem is reprogramming them when their internal oscillator is
>
> > set to run. Someone mentioned that, so I'm not taking credit. As
> > soon as you plug them into the JDM they get VDD and VSS so they
> start
> > to run.
>
> In my experience
> - the Vpp before Vcc sequence is (only) needed when you use internal
> /MCLR
> - problems with the oscillator indicate that the rise time from 0 to
> Vpp
> is too slow
>
> Wouter van Ooijen
>
> -- -------
> Van Ooijen Technische Informatica: www.voti.nl
> consultancy, development, PICmicro products >


__________________________________




> where do you get the programming voltage specs and sequences? I
> perused the mid-line reference catalog and the device data sheets, and
> I don't see where the specs are listed . . . thanks.

the programming specifications are in a separate document with the
obvious title. It is shown in Microchips page on each device.

Wouter van Ooijen

-- -------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products