1. the ROM-DOS will refresh the watchdog after the 7188 first power on
2. the program use EnableWDT to tell ROM-DOS --> stop refresh watchdog
3. then this program will refresh watchdog
4. the user can press any key to stop refresh
5. the watchdog timer is fixed at 1.6 sec --> after 1.6 sec the 7188 will reset
6. if the user PRESS ANY KEY before 1.6 sec --> this program use DisableWDT
   to tell ROM-DOS to refresh watchdog again --> 7188 will not reset
7. in the rormal condition, the program will
   1. EnableWDT()
   2. continue refresh watchdog by RefreshWDT()
   3. before program stop, DisableWDT()