Hello Mr. raja sekhar,

The MAX186 Serial 12-bit ADC is pretty
straight forward to use. Hook up the
following circuit, bang out some
assembly software and viola you have
instant ADC. I have used it extensively with
good results.



The below web sites have more information.

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http://www.maxim-ic.com/appnotes.cfm/appnote_number/1108
Understanding Single-Ended, Pseudo-Differential and Fully-Differential ADC Inputs
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http://www.maxim-ic.com/appnotes.cfm/appnote_number/119
12-Bit ADC Upgrades µC's Internal 8-Bit ADC
==============================================================

Good luck,

Charles Bannister