Pack Multiple Fields into a 16-bit Control Register

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

#define MODE_POS 0
#define SPEED_POS 3
#define RESERVED_POS 8
#define STATUS_POS 10

/* Field masks */
#define MODE_MASK 0x7
#define SPEED_MASK 0x1F
#define RESERVED_MASK 0x3
#define STATUS_MASK 0x3F

#define SET_MODE(val) (((val) & MODE_MASK) << MODE_POS)
#define SET_SPEED(val) (((val) & SPEED_MASK) << SPEED_POS)
#define SET_RESERVED(val) (((val) & RESERVED_MASK) << RESERVED_POS)
#define SET_STATUS(val) (((val) & STATUS_MASK) << STATUS_POS)

uint16_t pack_register(uint8_t mode, uint8_t speed, uint8_t status) {
    return SET_MODE(mode)| SET_SPEED(speed)|SET_RESERVED(0)| SET_STATUS(status);
}

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;
}