Need help with schematic for jdm pic programmer

[Lessie]

Does anyone know how the circuit diagram of the jdm
pic programmer work? How is it possible that Vdd is
connected to GND(7)??
Please help, the circuit is here:
www.piclist.com/techref/microchip/devprogs.htm
about 5 screens down.
thanks.

 

[Bill Bowden]

Lessie wrote:

Does anyone know how the circuit diagram of the jdm
pic programmer work? How is it possible that Vdd is
connected to GND(7)??
Please help, the circuit is here:
www.piclist.com/techref/microchip/devprogs.htm
about 5 screens down.
thanks.

I think RTS supplies a negative voltage, so
the PIC sees Vdd at +5 more than Vss because
of the diode (D2). So, ground on the connector
is actually 5 volts higher than RTS.

-Bill

 

[Lessie]

I think RTS supplies a negative voltage, so
the PIC sees Vdd at +5 more than Vss because
of the diode (D2). So, ground on the connector
is actually 5 volts higher than RTS.

Hi, thanks for your reply.
One more point, the 12V supply for programming, shouldn't
there be a capacitor there somewhere, to smooth out the
clock (RTS), i.e. like C1 ?