Hi,

It was the board having problem. The ADC channel being measured was getting mixed with adjacent channel, which reads temperature from AD590 through a couple of op-amps. Somewhere there is a wrong connection on the entire board. Replacing the board has worked at the moment.

Still I don't know at all how it worked with 89V51RD2. Solving the actual problem is a task but kept aside for the time being.

Thanks for your help.



p.s. I have not vanished after getting help from forum. I have posted my concluding feedback here and will post more later if I get the true cause of this problem.