As you might know the PIC microcontrollers have built in hardware watchdog timer peripherals. They have to be configured with the configuration bits. When using the bootloader on the SBC65EC and SBC68EC boards, the configuration bits can not be changed. The configuration bits are programmed together with the bootloader. When updating the firmware (or writing your own code) via the Modtronix Network Bootloader, you can not change the configuration bits. The configuration bits on both the SBC65EC and SBC68EC boards have been set up so the watchdog timer can be enabled by using the SWDTEN bit.
On the SBC65EC the watchdog timer has been configured as follows:
Watchdog disabled (SWDTEN controlled), Watchdog prescaler = 128. This gives: min=435ms, typ=512ms, max=589ms
On the SBC68EC the watchdog timer has been configured as follows:
Watchdog disabled (SWDTEN controlled), Watchdog prescaler = 32. This gives: min=224ms, typ=576ms, max=1056ms
This means, that by setting the SWDTEN bit in the WDTCON register, the watchdog timer will be enabled. After enabling the WDT, the CLRWDT() function must be called at a regular basis. If not called for 435ms (min) for the SBC65EC, or 224mm (min) for the SBC68EC, the board will reset. This has already been done in the Modtronix Web Server code via the FAST_USER_PROCESS() macro in the "projdefs.h" file. This FAST_USER_PROCESS() macro is called in many places in the code where the program could delay for more then the WDT configured times.