Pack Multiple Fields into a 16-bit Control Register

Code

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

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
   uint16_t reg = 0;
   
   uint16_t nxt_reg = reg | (mode & 0x07);

    // for speed
   uint16_t sp_len = 5;
   uint16_t sp_pos = 3;

    uint16_t mask = (1U<<sp_len)-1;
    uint16_t speed_val = (speed & mask)<<sp_pos;
    uint16_t nn_reg = nxt_reg | speed_val ;

    // for res
    uint16_t res_len = 2;
    uint16_t res_pos = 8;

    uint16_t res_mask = ((1U<<res_len) -1)<<res_pos;
    nn_reg &= ~res_mask;


    // for status
    uint16_t  st_len = 6;
    uint16_t st_pos = 10;

    uint16_t mask_st = (1U<<st_len)-1;
    uint16_t status_val = (status & mask_st)<<st_pos;
    uint16_t final_reg =  nn_reg | status_val;

    return final_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;
}

Solving Approach