Hi,

The USART module of a PIC has multi-processor communication
capability using 9-bit address detection.

See this document:
http://www.datadog.com/rs485.pdf

Use The PC's UART With 9-Bit Protocols
http://www.elecdesign.com/Articles/I...ArticleID=6245
(You will have to wait 20 seconds before you see the doc).

See the datasheet of the used chip.

Best regards,

Luciano