i am interfacing mcp3551 with 89c51. i have the problem that the count is not stable. i want the header file for mcp3551 with 89c51. please help me, its urgent.........
"can anyone suggest me any specific circuit through which i can get low noise."
"this requires low-noise, high-precision, careful analogue design - that's not something that can be rushed!"
So, NO; nobody can just give you a quick, simple, specific, answer - it is a matter of skilled, careful, design.
Have you checked the Microchip website for design guidance?
Also look at the sites of other ADC manufacturers for their guidance - the techniques will be generally applicable.
And remember: it has nothing to do with Keil software tools!