thanks peter.. i setup the 89c51 with all necessary circuit..... what's happening is that when i program and run the HEX file which blinks the LED and which i have downloaded from the internet it works fine.... but when i compile and run the program with SDCC compiler then it does not run. i used the same set up for both Runs. so wrong connections can not be the reasons. what i suspect is that SDCC is not compiling the code for 89c51 although its working fine on 89c2051. its only my speculation as i have not tested other compilers.

is there any indication by 89c51 that its running my code other than the LED ?????

Shahzad