The common example for running a watchdog timer on mbed processors doesn't work for the LPC1114, a common and easily-breadboardable ARM chip. My program provides a watchdog class that works on the LPC1114 but which is also similar to the common example found in https://mbed.org/forum/mbed/topic/508/

Dependencies:   mbed

Revision:
0:1c1e04c41063
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Aug 10 02:58:11 2014 +0000
@@ -0,0 +1,68 @@
+#include "mbed.h"
+
+/*
+Main code copied from: http://mbed.org/cookbook/WatchDog-Timer
+Modified for use with LPC1114 with source code found here:
+https://github.com/mbedmicro/mbed/blob/master/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC11XX_11CXX/LPC11xx.h
+With some inspiration from:
+https://github.com/Mrjohns42/RSL/blob/master/LPC1114/nRF24L01/wdt.c
+*/
+
+// LEDs used to indicate code activity and reset source
+DigitalOut led1(dp1);
+DigitalOut led2(dp4);
+ 
+// Simon's Watchdog code from
+// http://mbed.org/forum/mbed/topic/508/
+class Watchdog {
+public:
+// Load timeout value in watchdog timer and enable
+    void kick(float s) {
+        LPC_SYSCON->SYSAHBCLKCTRL = LPC_SYSCON->SYSAHBCLKCTRL|(1<<15);
+        LPC_SYSCON->WDTCLKSEL = 0x1;                // Set CLK src to Main Clock
+        LPC_SYSCON->WDTCLKUEN = 0x01;       /* Update clock */
+        LPC_SYSCON->WDTCLKUEN = 0x00;       /* Toggle update register once */
+        LPC_SYSCON->WDTCLKUEN = 0x01;
+        LPC_SYSCON->WDTCLKDIV = 0x10;
+        uint32_t clk = SystemCoreClock/16;    // WD has a fixed /4 prescaler, PCLK default is /4
+        LPC_WDT->TC = s * (float)clk;
+        LPC_WDT->MOD = 0x3;                   // Enabled and Reset
+        kick();
+    }
+// "kick" or "feed" the dog - reset the watchdog timer
+// by writing this required bit pattern
+    void kick() {
+        LPC_WDT->FEED = 0xAA;
+        LPC_WDT->FEED = 0x55;
+    }
+};
+ 
+// Setup the watchdog timer
+Watchdog wdt;
+ 
+int main() {
+    int count = 0;
+    // On reset, indicate a watchdog reset or a pushbutton reset on LED 4 or 3
+    if ((LPC_WDT->MOD >> 2) & 1)
+        led1 = 1; else led1 = 0;
+        
+    // setup a 10 second timeout on watchdog timer hardware
+    // needs to be longer than worst case main loop exection time
+    wdt.kick(10.0);  
+ 
+    // Main program loop - resets watchdog once each loop iteration
+    // Would typically have a lot of code in loop with many calls
+    while (1) {
+        wait(.1);
+        led2 = 1;
+        wait(.1);
+        // Simulate a fault lock up with an infinite while loop, but only after 25 loop iterations
+        if (count == 25) while (1) {};
+        
+        // LED 2 will stay on during the fault
+        led2 = 0;
+        count ++;
+        // End of main loop so "kick" to reset watchdog timer and avoid a reset
+        wdt.kick();
+    }
+}
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