Hi andi,

if this is the code you're using:

start :
mov p0,#55h
mov p0,#55h
mov p2,#aah
mov p2,#55h
sjmp start

then I see why it doesn't work:

1. writing twice #55h to port 0 doesn't change anything,

2. you can't write to P2. It is used to access external memory. Better use P3, then it will work

Good luck!

Juergen