NETMF C# hardware Watchdog for FEZ Cerb40

Hardware watchdog is very important in industrial control. The FEZ Cerberus main board   /FEZ Cerb40 module are good choose for low cost design. Unfortunately, it is not support watchdog in firmware! (also, The GHI guy said :  Open Source "OSHW" is not support!)

I read the STM32F405 reference manual to find out the solution ... And I try to write the low leve CPU register setting to enable watchdog ...  It is working ! 

The C# source code as follows :
using System;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using GHI.OSHW.Hardware.LowLevel;
 class iWatchDog
    {
        public uint  TimeOut = 4000; // default 4000 units    
        private uint AccKey = 0x5555;
        private uint RstKey = 0xAAAA;
        private uint EnableKey = 0xCCCC;
        //----------------------------------------------------------------
        Register IWDG_KR  = new Register(0x40003000);
        Register IWDG_PR  = new Register(0x40003004);
        Register IWDG_RLR = new Register(0x40003008);
        Register IWDG_SR  = new Register(0x4000300C);
        //-----------------------------------------------------------------
        public void Init()
        {
            IWDG_KR.Write(AccKey);   // open the access key
            IWDG_PR.Write(4);        // write the Prescaler for 2ms (One unit)
            IWDG_KR.Write(AccKey);   // open again
            IWDG_RLR.Write(TimeOut); // write the down counter  
        }
        //--------------------------------------------------------------
        public void Enable()
        {
            IWDG_KR.Write(AccKey);    // open access key
            IWDG_KR.Write(EnableKey); // enable counter
        }
        //---------------------------------------------------------------
        public void Reset()
        {
            IWDG_KR.Write(AccKey);    // open access key
            IWDG_KR.Write(RstKey);    // reload counter
        }
    }


//--------------------------------------------
// your main program as follows:
//--------------------------------------------.
.
 iWatchDog Wdog = new iWatchDog();
 Wdog.TimeOut = 2500; // for 5 second time out
 Wdog.Init();
 Wdog.Enable();  // enable watch dog
.
.
//-------- the easy way to reset the watchdos counter -----------------
  void timer500_Tick(GT.Timer timer)// 500mS timer tick
  {

             Wdog.Reset(); // reload the watchdog timeout counter
  }