[HH] arduino help: write protect, USB FTDI, ICSP, all connect to reset

[Greg London]

I wanted to incorporate an arduino into a design I'm working on.
But I didn't want a "duino" board connected to my design,
I wanted an atmega328 chip as part of my design.

I am starting with the following schematic for a bare bones arduino:

http://thetransistor.com/wp-content/uploads/2010/02/Minimalist-Arduino-Rev01-Schematic.pdf

I wanted to keep the two connectors for ICSP and the USB FTDI
so I can program the bootloader and also connect to it via USB
and download arduino code.

But I can't seem to figure out the reset connections between
the two headers and the atmega328.

Somewhere, and I can't find it anymore, I read that the atmega328
has a "write protect" or some sort of bit like that on it.
And that if this bit is set, you can't program the bootloader.
To clear this bit, I thought I remember reading that you had to
put 12v on the reset pin of the atmega328.

Anyone know if this is correct?

Anyone have a URL to a site that explains this?
cause I can't find that website I was reading before.

So, I wanted to make sure I could put 12v on the reset pin to the
atmega328 but isolate it so I don't accidentally fry whatever
might be connected to the USB FTDI or the ICSP headers.

Yeah, I could just disconnect the header, but I was thinking I
might solder in the USB FTDI interface because I will want
to be able to reprogram my board.

Anyway, I'm adding some 0.2v diodes to the schematic between
the voltage regulator and the USB FTDI and the ICSP so that
none of them accidentally fry the others with power supply
voltages being hooked up simultaneously.

I wanted to isolate the 12v to reset, but I don't understand
how the DTR/RST from the USB FTDI works when its connected
to reset via a cap.

And I wasn't sure how the ICSP header used reset either.

Does the USB FTDI reset the atmega328?
Does the atmega328 reset the USB FTDI?

How's the DTR/RST work that it's connected via a cap?

Does the ICSP reset the atmega328?
Does the atmega328 reset the ICSP?

Does the ICSP put out the 12v to clear the write protect bit?

If anyone has some URL's with some decent specs for what
the USB FTDI signals do and what the ICSP signals do,
that would be greatly appreciated.

Thanks,
Greg