Started by Lee September 10, 2003
Yet another 16F877 problem unfortunately, but hopefully a simple one
(for some nice person to answer)...

I have the equivalent of PICSTART plus (with MPLAB). I've attempted
to write to the PIC, but it fails. I get several "serial time-out's"
and the occasional "memory is protected". As far as I know, I've set
the config bits correctly, and have tied RB3 to GND via a resistor to
disable LVP.

So, nothing on the chip is changing. Just for completeness, the
lights go on/off as they're supposed to.

If anyone could point me in the right direction, or in fact knows
what the problem is, I'd be very grateful for your help.

Lee :-)



Have you checked the actual voltage going to the Pic?

Colin
--
cdb, on 11.09.2003

I have always been a few Dendrites short of an Axon and believe me it
shows.

Light travels faster than sound. That's why some people appear bright
until they speak!



I have checked. The chip is powered right. The MCLR' isn't rising to
the programming voltage.

Should this be a constant voltage throughout programming? If so, I'll
apply it externally. Unless you know of any problems doing that.

Thanks a lot.
Lee
--- In , cdb <cdb@b...> wrote:
> Have you checked the actual voltage going to the Pic?
>
> Colin
> --
> cdb, bodgy1@o... on 11.09.2003
>
> I have always been a few Dendrites short of an Axon and believe me
it
> shows.
>
> Light travels faster than sound. That's why some people appear
bright
> until they speak!





The MCLR voltage for programming has to be constant around 13.5v.

If this chip is incircuit make sure you put an isolating diode
between the 5v supply and your 13v supply otherwise the pic and the
circuit it is attached to make go bung.

Anode of diode to +5v supply, Cathode to MCLR pin Programming voltage
goes to this junction. Good idea to have a 10K approx resistor
between Anode of diode and +5v supply to make sure MCLR is pulled up
on reset.

Also check that you haven't in the configuration file set the MCLR
pin as an input.

Colin
--
cdb, on 13.09.2003

I have always been a few Dendrites short of an Axon and believe me it
shows.

Light travels faster than sound. That's why some people appear bright
until they speak!