Low voltage at controller output

[Sounak Das]

I have an AT89S52 development board with 11.059MHz oscillator and a 220V to 9V 750mA step down transformer for power supply which is rectified and regulated and fed to the board. when i am programming the controller with a led blinking code the out put is varying from 2.8V to 1.8V where it should varry from around 5V to 0V. please suggest me a way to overcome this problem. 

[dagakshay]

check the input voltage at pin 40 with repect to pin 20….

on which port you getting this output… 

[Amit Joshi]

Check the voltage difference b/w ground and vcc pins. make it sure are you giving high voltage at EA/VPP pin

[Author]

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