The user should always precede a read of any status registers with a write. The byte written to the register implies which bits the user wishes to read. The user should write a byte to these registers with a one in the bit positions he wishes to read and zero in those bit position where the latest information is not required. When one is written to a bit location, the read register is updated with the latest information. When a zero is written, the read register is not updated but the previous value is held. A write to the status register is immediately followed by a read of the same register.
FFh can be written to SRx registers to read the actual value.