In input mode, the pin voltage level is passed through a meta-stability protection circuit and translated to a logic level. The pin logic level is readable using the DATA_RO registers or the INT_STAT register.
In the latter case, the direction control must be set to 0 for the input from the I/O pad to be passed through to the register. There are two APB address locations allocated to the pin: A read only location for the dedicated path and a read/write location for the registered path. The pin value can be read from either location in the input mode. The two paths produce different values in the output mode with inactive output enable.