On 2010-08-04 01:30, David Duffy (AVD) wrote:
> On 4/08/2010 8:19 AM, Jan-Erik Soderholm wrote:
>> On 2010-08-03 23:15, David Duffy (AVD) wrote:
>>
>>> One thing is still not perfectly clear - does the ICSP need to cycle
>>> Vcc to program the chip? My limited testing showed that it did not, but
>>> is this true for all chip families? David...
>>>
>>>
>> As I understand it, controling Vdd(*) is (only ?) needed when
>> re-programming a PIC that has been config'ed with "Internal-MCLR".
>> If you do not use that config-option, the programmer usualy do
>> not need to cycle/control Vdd since it can get "control" of the
>> PIC using the MCLR line only.
>>
>
> Ah, that makes sense. I usually use the "Internal-MCLR" option now,...

And that puts special demands on the sequence of Vdd and Vpp. Which
usualy also meens that the programmer must control Vdd. The problem
is that, since there is no external MCLR, the programmer can not
hold the processor in "reset" mode (MCLR at GND level) and then
apply Vpp directly (whithout the processor beginning executing).

> either because I use that pin as an input, or so I can tie it low seeing
> it's next to Vss on most chips I use.
>
> Moving to ICSP with SMD chips means I can probably use large pin count
> devices to make up for the otherwise lost (to ICSP) pins.
> David...
>
--=20
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