>Somehow I got confused with the open drain.
>Is there a graphical representation to facilitate understanding?

Imagine a switch that connects the "open drain" terminal to ground.
That is it, in its simplest form.

It is common for devices to be able to sink more current than
they can source.  This is why many circuits (lights, for instance)
are connected between the supply and an open drain pin.

A "source" is defined as something with an unlimited supply.
A "sink" is something you can run unlimited current into.  In
the real world these things
do have limits, and those are on the spec sheet.


>Pull-Up resistor, or simply pull-up?

This can be either, since usually it is a resistor, but there are
cases where they are active parts (like the weak pullups in a PIC)
in which case it's better just to stick to "pullup".

>Pull-down

Same thing execept the other end is tied to ground rather than
the supply.

Barry

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.