I read Olin's post as that he was talking about Vpp-before-Vdd
(which is harder to implement on self-powered targets). Not the
level as such of Vdd (that very well might be another problem,
of course).

Jan-Erik.


Bob Axtell skrev:
> Wouter van Ooijen wrote:
>>>> For an ICSP programmer it makes of course sense to draw the 
>>>>       
>>> power from
>>>     
>>>> the target itself.
>>>>       
>>> But then the programmer can't control Vdd, which is necessary for some
>>> chips.  In many instances a hobby programmer can get away 
>>> with using target
>>> Vdd, but serious professional programmers can't afford to do that.
>>>     
>> ICSP and variable-voltage verification is a shaky combination anyway....
>>
>> BTW: which chip require variable Vdd for programming (!= for
>> verification)?
>>   
> NOBODY requires that for hobbyist use. The main problem is that USB 
> ports are allowed to drop their
> voltage to 4.3V legally, and while most PICs will program at that 
> voltage, few will execute a bulk-erase, which is
> the main problem with most USB programmers.
> 
> --Bob
> 
>> Wouter van Ooijen
>>
>> -- -------------------------------------------
>> Van Ooijen Technische Informatica: www.voti.nl
>> consultancy, development, PICmicro products
>> docent Hogeschool van Utrecht: www.voti.nl/hvu
>>  
>>
>>   

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