What are Locks bit 1,2,2 in 8051

[mohamed saleh]

hello
i have atmel 8051 "AT89s52" chip
i used to program it with isp-prog from www.8052.com
but when i wrote lock bits 1 ,2 ,3 to it
i wasnt able to program it any more
so what are these bits
and how i can get rid of them to be able to program my controller again
and what is "fuse bytes"

thanks

 

[yaharoni]

these bits
bloks reading flash so the device can't be duplicated
to modify prog u shuld erase ALL flash content
and program it again

yuv