[Milkymist-devel] How does Hot Plug Detection(HPD) work ?

[Sébastien Bourdeauducq]

On 02/08/2012 05:30 AM, Werner Almesberger wrote:
>> s1, let's connect J17.HPD pin to one un-used pin on fpga directly.
>
> I'd add a series resistor, since I don't think the FPGA's pins
> are 5 V tolerant,

A series resistor alone is not enough, there are no clamp diodes to 
VCCIO in the FPGA. We should add one, or even better, send that signal 
through some buffer (2N7002, gate, ...).

> Also, VD1 on http://www.dzsc.com/data/html/2009-6-15/76847.html
> looks like a good idea. Else, a monitor might even reverse-feed
> the entire M1.

On the other hand, this is overkill.

S.