Hello,
According to this: http://www.8052.com/tutsfr.php , the sfrs whose address are divisible by 8 are bit addressable. You can do things like SETB or CLR on them. But aren't they overlap other memory addresses? I mean, for example, P0 is in 80h. So P0.0 will be 80h, P0.1 will be 81h. But 81h is the address of SP. Aren't they overlap?
P0.0 and P0.1 only refers to individual bits of the 8-bit P0 register (from what I understand).
You are confusing a bit address with a byte address. They do not overlap or refer to the same physical location. Instructions that take bit addresses (eg. SETB) know how to decode the bit address into a byte address and bit number. The byte address is obtained by masking out the 3 lowest bits in the bit address. The bit number is obtained by masking out the highest 5 bits.
eg. bit address 87h --> byte address 80h, bit #7