Does the state of I/O need to be initialized before its special function is enabled?
some of ports need to be initialized before its special function is enabled. For example, the related I/O port should be set as input before the external interrupt input is enabled; similar to the capture input ports, serial communication interface ports. While part of ports don”t need to be initialized before their special functions are enabled, such as ADC input, DAC output, voltage comparator function, Buzzer output, PWM output and compare output.
