c++ - ASM I/O pins HCS12 micro controller -

iam using hcs12 micro controller. following program have takes input on board keypad , displays letters on board lcd depending on key pressed (i attached portion of code dealing inputs / outputs, can attach rest if need easier on eyes way).

what rid of keypad being used inputs, , use sensor have sends active low signals though 3 separate pins instead. way in stead of having push keypad each time, whenever sensor reads 1 of readings (either porta1, 2 or 3) display correct letter.

the init_keypad function sets porta0-porta3 inputs.

in getkey function im not sure how change if statements read porta0-porta3 individualy

void init_keypad(void){     ddra = 0xf0;  // pa7-pa4 output; pa3-pa0 input     ddrb = 0xf0;     pucr |= 1;   // pupae =1 (enable pull-up on porta inputs)  }  char getkey(void){     porta = 0xe0;       // selects row 0          if ((porta & 1) == 0){     cmdwrt(0x01);       delay(20);       if ((porta & 1) == 0) return('l');//true if '1' key still active after 20 ms     }     porta = 0xd0;     if ((porta & 1) == 0){     cmdwrt(0x01);       delay(20);       if ((porta & 1) == 0) return('s');//true if '1' key still active after 20 ms     }     porta = 0xb0;       if ((porta & 1) == 0){     cmdwrt(0x01);       delay(20);       if ((porta & 1) == 0) return('r');//true if '1' key still active after 20 ms     } 

let's assume you've read input porta variable we'll name input.

in case, testing individual bits of input looks like:

if (input & 1) {     // bit 0 set } if (input & 2) {    // bit 1 set } if (input & 4) {    // bit 2 set }