thanks to all for concerened reply.

dear raghu

i need to clarify things,i.e

1.i meant "" supplying 5v as Vcc to the ADC 0808 "" not to the EOC pin.

2.as i saw the timing digrams in the datasheet, the EOC pin remains high during conversion and goes low signalling the conversion is completed , not vice versa as u said.

i'll try with fixing the time delay as u said.
i tried ""free running mode ""operation by tying the SOC and EOC pins. (ALE=5v,OE=gnd)
but this also doesn't work. i suspect this to be a specific chip problem and will try it in a new one

ilancheliyan