#include <stdio.h>

int main(void)
{

   unsigned short value1 = 0x421F;

   unsigned char byte1 = (unsigned char)(0x00FF & value1);
   unsigned char byte2 = (unsigned char)(0xFF00 & value1);

   printf("value1: %04X\n", value1);
   printf("byte1 : %02X\n", byte1);
   printf("byte2 : %02X\n", byte2);
   return 0;
}

value1: 421F
byte1 : 1F
byte2 : 00