A convenient method to implement friendly code uses bit-specific addressing. Using this, individual pins of a port can be accessed independently. This feature is available on the Texas Instruments TM4C line of microcontrollers. This bit-specific addressing works on the parallel port data registers. Given the base address for Port A is 0x4000.4000, the bit-specific address of all pins in Port A are shown below. #define PA7 (*((volatile unsigned long *)0x40004200)) #define PA6 (*((volatile unsigned long *)0x40004100)) #define PA5 (*((volatile unsigned long *)0x40004080)) #define PA4 (*((volatile unsigned long *)0x40004040)) #define PA3 ("((volatile unsigned long *)0x40004020)) #define PA2 (*((volatile unsigned long *)0x40004010)) #define PA1 (*((volatile unsigned long *)0x40004008)) #define PAO (*((volatile unsigned long *)0x40004004)) Specify a #define PA71 that allows us to access bits 7 and 1 of Port A. (*((volatile unsigned long *)0x40004208))