Prahlad:
I almost voted -1 on your posting. Not because of the work you clearly went to prepare the graphic and all.....but because there is a better solution than you show (particularly if the application the original poster has at hand is a one-up installation). That solution is to use an RS485 multi-drop interface. Using this approach there no need to fabricate up a whole 8052 buffer / mux assembly like you showed. Instead one just buys an RS485 adapter for the PC end COMM port. If the 10 target slave devices are under design control then the ports on those devices are easily changed over from RS232 transceiver chips to RS485 chips. If the target slave devices are an existing design then they are equipped also with off the shelf adapters.

The software to control the overall structure of the RS485 multi-drop interface is probably simpler than the scheme you proposed and would certainly be more straightforward than introducing the intermediate device.

Michael Karas