Pack Multiple Fields into a 16-bit Control Register

Code

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

typedef union {
    uint16_t REG_VAL;
    struct {
        unsigned mode     : 3;
        unsigned speed    : 5;
        unsigned reserved : 2;
        unsigned status   : 6;
    } bits;
} REG;

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    // Your logic here
    REG R;
    R.bits.mode = mode;
    R.bits.speed = speed;
    R.bits.status = status;

    if (R.bits.reserved == 0) {
        return  R.REG_VAL;
        }
        else{
            printf(" RESERVED BITS DIFFERENT OF '0'");
        }
        }

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;
}

Solving Approach