Another way to deal with this issue is to convert over to using RS485 communications. A serial port from the microcontroller can then multi-drop to several serial peripherals.

If you have an existing setup all currently implemented in RS232 you can visit the web site of B&B Electronics and review their wide array of RS232 to RS485 converters.

When using RS485 communications it will be necessary to properly structure the software of the master port to interact correctly with the other two devices as slaves.

Michael Karas