i used atmel 89C55WD instead of intel 87C52 with the same code but it didnot work .
after comparing electrical characteristics i found that the drive capability of both micros differ very much
port 0 of intel can sink and source 7 mA
whereas atmel can sink 3,2 mA and source 0,8 mA

it is very annoying to find that the compatibles are not really compatibel

is it possible to increase source current of atmel ?