i made a program to blink LEDs on port 2... with uVision (BlinkLED.c) for on-chip 89C51 (4kbROM,128byteRAM) and it work well on uVision simulator but.. when i compile it, send the .Hex to the devBoard, it only run the initial command (after void main, before while(1)) i light 1 LED on P1.3 and it do fine... whats wrong with that? is it the setup matter? how can i setup uVision for my 89c51 on-chip EEPROM? is any one can help me... ive try it many time, but still dont work.. Thanks. Best Regards, Andy Mario