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March 25, 2005, 11:33 pm
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I have been messing with picstart again. I use it mainly for isp programming
often it fails.
so I got fed up with this and started to wonder why.
I have always used a 10k pull up on mclr and a diode.
http://www.dessy.ru/kitlab/PICSTARTER+.html on pins 1/ 4/ 14/ 32/ 40
from there I got a schematic and noticed that mclr is pulled low with a 5.1k
so I my pull-up
is now 33k
because I think the 10k was not being pulled low enough and not allowing pic
What value resistor do you use as a pull up on mclr ?
Re: Picstart plus
After reprogramming my devices need to be resetted,
so I don't have any timing difference or lock-ups when one of the devices is
I have several devices on the same MCLR which is pulled high by a MRS of
by selecting which program lines to be used (analog switches) I can decide
which device to be programmed. But only the PGC and PGD are switched this
Also al other chips (except the chips needed for programming) are disabled
when MCLR goes low or above VPP(min).
When the chips go "online" again the mcu start finding each other and other
chips for a full system check, only if passed they will go in normal usage
When I checked the design I also used an MRS of 1k5 on a bread board simply
because it was in front of me.
So don't bother to much about this pull-up but simply try some, if it goes
wrong with programming check TFM (the @#$% manual) of your programmer for
The difference lies most of the time with the programmer and how much the
can drive low or high.
Greetings and good luck
Alexander (which has the bad habit of doing some overkill)
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