code: def u64_to_hex16le(val):
      
      return ''.join("%02x" % (x & 0xFF) for x in (
          val,
          val >> 8,
          val >> 16,
          val >> 24,
          val >> 32,
          val >> 40,
          val >> 48,
          val >> 56,
      ))
docs: ! @brief Create 16-digit hexadecimal string from 64-bit register value