RS485 with +-15V common mode

Jens Hildebrandt wrote:
> 
> Ralph Malph wrote:
> 
> > Boy, I thought it was tough finding an I2C port expander chip that fit
> > all my requirements.  I am looking for an RS485 tranceiver that I can
> > use along with an RS232 chip to allow either protocol through the same
> > pins.  But I can't find an acceptable chip anywhere.
> >
> > This was discussed a few weeks ago, but I don't think anyone mentioned
> > any part numbers that were compatible.  I think I can find an RS232 chip
> > that will tristate the outputs, but I can not find a full duplex
> > RS422/RS485 chip that is +- 15 volt tolerant.
> >
> > Anyone actually done this before?
> 
> I just remember the MAX3160/3161. You can switch this part between  RS232 (
> 2Rx/2Tx) , Full-Duplex RS485 or Half-Duplex  RS485. RS232 and RS485 mode use the
> same pins and according to the datasheet they allow +/-25V input voltage.

Yes, Sipex and Linear Tech also make this sort of part.  But they all
charge a lot for them.  That is why I am looking for a two chip (three
actually) solution.