> G'day all.
>
> I am about to add a SMT 12C508 to a board layout and was wondering
> what others are using for ISP connectors.  The databook appears to
> suggest a single row 5 pin header, but makes no mention of pin
> assignments.  Is there any kind of formal or informal standard or
> should I just go with is easiest to route.  Since this is the first
> of many boards with a pic ISP header, I want to get it right the
> first time.


Tjaart mentioned powering pins 1, 4, 7, 8.  You might also consider
adding a diode from your boards 5v supply to the MCLR/VPP line to
prevent the 13 volts programming signal to clamp onto your power
supply, you might also consider a small resistor to the programming
data and programming clock lines.  Use these two lines as switch
inputs or something similar in your design, so they don't have a load
on them.  If they are driving some low impedance load your programmer
will have a devil of a time driving them.

If you want to vary the power supply voltage (recommended) and verify
at different voltages, you'll have to include a beefy, adjustable
power supply.,  and if the setup is slick and automatic it will be
under software control from your PC.  This all gets pretty complex.
If you are doing one of a kind prototypes skip this altogether.

The bed of nails is a good idea for high volume stuff.  Bed of nails
are not expensive to build, just time consuming.  Let me know if you
need sources for spring pin contacts.  For low volume stuff just use
a header.




-- Lawrence Lile

     "The ideal design has zero parts"  -
            (attributed to Harold Hallikainen)

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