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'[PIC]: ICSP Question'
2001\10\01@110517 by Ron Hackett

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Hi all,

I have an ICSP question I hope someone can shed some light on.  I am using
the ICSP connector on my Warp13 programmer with a 16F84, and I find that the
Warp software reports multiple errors if the +5V to the PIC comes from my
circuit.  If I disconnect my circuit +5V and power the PIC from the
programmer, the chip programs fine, but I can't execute the program until I
switch the +5V back to the circuit supply.  (MCLR is isolated with a diode
and a resistor.)

I can live with this if I have to, but if there is any way to avoid the
repetitive shifting of the +5V supply back and forth, it would certainly
simplify things.  Any suggestions?

Thanks...  Ron

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2001\10\04@024850 by Anand Dhuru

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Ron, I faced precisely the same problem with my EPIC programmer. The
solution might sound horrendeous, but is actually safe, and proven to be
working fine.

The EPIC uses a transistor to switch the +5 volts to the PIC only during
read / write ops.

In my case, since the target circuit had very few components besides the PIC
itself, I wanted to power it up with the 5 volt regulator on the EPIC
itself. This did not work reliably, exactly as what you have described. The
solution was to short the collector and the emitter of the switching
transistor. I realize this sounds wierd; the transistor is now apparently
serving no purpose. But it works like a charm. Even resets the PIC after
each write cycle.

Regards,

Anand

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2001\10\04@050704 by Roman Black

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In most cases you can do ICSP with the PIC
permanently powered up. I do a lot of my
projects this way using a PicStart Plus.
When not programming, the PSP keeps the
PIC in reset, (MCLR low) it then goes to
MCLR at 13v to do the program and verify etc.

If you add a switch on MCLR to connect it
to 5v instead you can simply flip the switch
and run the program in the PIC.

I have one of these setups on a protoboard
(the white plug in ones) and can just leave
MPLAB running, flip the switch, press "program"
on MPLAB and then flip the switch back to run
it. Very cheap setup and great for small PICs
(16F84) in development.
-Roman




Anand Dhuru wrote:
{Quote hidden}

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