Hello,

May I add some questions here?

 >The idea is that
> you avoid powering up the part until you're ready to program it; you
> have to raise both simultaneously or nearly so, so that the program on
> the chip doesn't start running before you get it into programming mode.

 From Microchip's PIC12C5XX Eprom Memory Programming Specification
(DS30557D p.5):
"The MCLR pin should be raised from Vil to Vih within 9 ms of Vdd rise".

 From Microchip's PIC12C67X ICSP Programming Specification
(DS40175C p.4):
"The MCLR pin must be raised from Vil to Vih before Vdd is applied".

1. Is it really important to use these different strategies for different
parts?
Isn't it always possible to apply the Vpp first and then apply the Vdd?
Say, in case of an in-circuit programming, apply the Vpp and then
switch on the target device. Is it safe to have Vpp ON and Vdd OFF for a
"long" time?

> (Unless you have disabled the power-on reset timer, you have 72
> milliseconds before the code starts to run.)

2. On the other hand, isn't 72ms quite a long time to not bother about these
Vpp BEFORE Vdd or AFTER?

Thanks,

Arkady

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