uVision 5 - 8051F580 compiler --> macro to make P4 bit addressable

The SFR P4 is at address 0xB5. This address is not bit-addressable. You can only set or clear bits by using AND / OR operators that modify the whole SFR with a Read-Modify-Write instruction. Example:

P4 |= 0x01;  // set bit P4.0
P4 |= 0x02;  // set bit P4.1

P4 &= 0xFE;  // clear bit P4.0
P4 &= 0xFD;  // clear bit P4.1

If you like, you can define macros for such expressions, but we don't have predefined ones.

The SFR P4 is at address 0xB5. This address is not bit-addressable. You can only set or clear bits by using AND / OR operators that modify the whole SFR with a Read-Modify-Write instruction. Example:

P4 |= 0x01;  // set bit P4.0
P4 |= 0x02;  // set bit P4.1

P4 &= 0xFE;  // clear bit P4.0
P4 &= 0xFD;  // clear bit P4.1

If you like, you can define macros for such expressions, but we don't have predefined ones.