On 24-Jan-02 Peter Onion wrote:
> On 23-Jan-02 Tim Webb wrote:
>> Is it ok to have capacitance between Vcc & GND during ICSP?
>
> Yes that is OK, and is probably essential as there is "stuff" going on inside
> the PIC (eeprom programming etc) that will still need a properly decoupled
> power supply.
>
> I think the issue is to do with capacitance on the pins used for ICSP (RB6,7)
> and the drive capability of the circuit driving them.

Having reviewed the ICSP Guide (30277b.pdf) there are issues about the amount
of "C" on the power supply lines as well.  Its worth a read as it covers
situation where the PIC is programmed in the application circuit.  The large
amounts of decoupling "C" can cause the rise time for Vcc to be too long if the
programmer can't supply enough current to quickly charge up these capacitors.

I guess if you are using a commercial programmer then you need to check how
quickly the supply does come up.  In my own programmer I actually switch the
+15V input of a 7805 so upto 1A is available to charge the decoupling
capacitors.

Peter.


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E-Mail: Peter Onion <ponion@srd.bt.co.uk>
Date: 25-Jan-02
Time: 15:58:38

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