One of the nice things that this approach gives me is some port
conservatism. However, since this design will sit on an RS-485 bus I think
I'm better off with a 16C72, which would give me the chance to fire up the
LED's on their own port. Then again, if I'm up to the task of the comms in
software, I could go with a 509 and use this method. A board with a MAX48x
and a 509 would make a nice small package (haven't looked at the port
possibilities yet). I'm trying to make this as small as possible.

-DO

[Everybody's replied - here's the latest]

> Yes, that was one of the things I found out some time ago too.  The reason
> behind this is that a LED behaves as a sort of a Zener-diode.  When it's
> off no electrical connection seems to exist between the two legs of the
> LED.  So, you can't use a LED in a circuit that should function as a
> Pull-up.  The way to go is to place a Pull-up (or down) resistor parallel
> to the LED (& series resistor), as you did/found out.
>
> Greetz,
>   Rudy Wieser
>