There are at least two things I can think of that can cause a reboot when
working with your LPT port. There is +5 volts being supplied by the PC on one
of the LPT pins. If this line should be loaded too heavily when you remove
power from your programmer, it may be enough to cause the PC to reboot.
Usually there is a protect resistor on this line to keep from doing any damage
to the PC, but a pulse COULD glitch it.

Also a spike created by removing power suddenly from your programer could
cause the PC to reboot. Proper care with diode strapping to +5 and ground on
all significant lines will help. Make sure you aren't using the +5 pin for
anything other than signal detecting.

Rick

Kajcsa Laszlo AIIV wrote:

> Hi,
>
> -strange thing happens
> -i have a homemade pic programmer(Bojan Dobaj type)
> -the power supply for it is a simple ac-dc power supply(mobile phone
> charger type 20V), which has no switch on the ~220V, you just have to pull
> in or out from ~220V
> -the programmer has a switch, which interrupts the + of the supply
> -if the programmer is connected to the LPT, and the + supply is
> interrupted and i pull out the ac-dc power supply from ~220V my computer
> is rebooting
> -the same thing is happening if the + supply is not interrupted
> -if the programmer is not connected to the LPT nothing happens
> -why?????????
>
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>
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