Hi Ashwin,

The problem with just tying two DB9s to a single MAX232 is that whatever is plugged into the two DB9s will conflict with each other. RS232 ports do not go to HI-Z when their not in use. If one is sitting at +12V and the other goes to -12V, assuming neither of them blows up, your MAX232 is going to see 0V.

You will need to use two MAX3223s. These have two control pins (FORCEON and ~FORCEOFF) that allow you to put the driver into the HI-Z state. They also have an ~EN pin that lets you put the receiver in a HI-Z state. Thus, you can turn on whichever one you're using at the time by setting and clearing the appropriate pins. These would also allow you to put multiple devices on a single RS-232 serial run. See data sheet at Digikey (http://rocky.digikey.com/WebLib/Te...X3223.pdf).

Good luck,

Joe