Hi Atrishekhar (Wow! I hope you can read that faster than I could type it.),

I can't put up a schematic for you because I still can't upload files to my area of the web site. But, its a simple enough schematic that I can describe it to you and you can draw it out. Still, even though it won't take long, you'd better hurry before the others start chatstising you for not searching first.

Start with three main components. 1) A DB9 connector. 2) A MAX3223 (you can use whatever kind you prefer, just verify the pin numbers by the pin name). 3) An AT89C51RC2 (or whatever 805x derivative µ-controller you're partial to, just take care to verify the pin numbers for your specific case).

You need three connections on the DB9 connector. Connect pin 2 of the DB9 to DOUT 1 (pin 17) of the MAX3223. Connect pin 3 of the DB9 to RIN 1 (pin 16) of the MAX3223. Connect pin 5 of the DB9 to GND. You should probably also connect the shroud of the DB9 to GND as well.

Now connect DIN 1 (pin 13) of the MAX3223 to TxD (P3.1; port 3 bit 1) which is pin 13 of the AT89C51RC2. Finally, connect ROUT 1 (pin 15) of the MAX3223 to RxD (P3.0; port 3 bit 0) which is pin 11 of the AT89C51RC2.

You will still need to provide power and ground along with decoupling and configuration capacitors for the MAX3223, or for whatever chip you're using, as per the data sheet. And if you're using a MAX3223 you will need to tie FORCEON (pin 14) to Vcc and ~EN (pin 1) to GND. Again, if you're using another chip, check for such requirements in your data sheet.

Hope this helps. Good luck. Now get ready for a boatload of chastisment for not searching first.

Joe