Pack Multiple Fields into a 16-bit Control Register

Code

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

#define FIELD(val,pos,len) (((val & ((1U << len)-1U)) << pos))

//FIELD(value,position,length) macro used.
// | operator to do each operation.
//Ensure bit values are proper
uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    if(mode > 7) mode = 7; //3 bits max
    if(speed > 31) speed = 31; //5 bits max
    if(status > 63) status = 63; //6 bits max
    return FIELD(mode,0,3) | FIELD(speed,3,5) | FIELD(status,10,6);
}

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