Pack Multiple Fields into a 16-bit Control Register

#include <stdio.h>
#include <stdint.h>

#define MODE_SIZE       3
#define SPEED_SIZE      5
#define STATUS_SIZE     6  

#define MODE_POS        0
#define SPEED_POS       3
#define STATUS_POS      10

volatile uint16_t control_reg = 0;  //Precaution ! reg may be writtenfrom anyhere: ISR/DMA/MemoryPins 

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    // Your logic here
    control_reg |= ((mode & ((1 << MODE_SIZE) - 1)) << MODE_POS);
    control_reg |= ((speed & ((1 << SPEED_SIZE) - 1)) << SPEED_POS);
    control_reg |= ((status & ((1 << STATUS_SIZE) - 1)) << STATUS_POS);
    return control_reg;
}

int main() {
    uint8_t mode, speed, status;
    scanf("%hhu %hhu %hhu", &mode, &speed, &status);

    uint16_t reg = pack_register(mode, speed, status);
    printf("%u", reg);
    return 0;
}