MCF52223. Is a solid watchdog possible on a MCF52223 MCU?

Discussion created by Claude_Sylvain on Feb 7, 2008
Latest reply on Feb 10, 2008 by Claude_Sylvain

Accordingly to the MCF52223RM.pdf Rev.3 document, section 11.5.4, first paragraph, it seem to be possible to configure de MCU watchdog to generate an hardware reset.

However, accordingly to the same document, same section (11.5.4), table11-6, CWRI bit field description, it seem that the only way to use the watchdog to reset the MCU is by configure it to generate an interrupt on watchdog timer time-out, and do a soft reset in the corresponding interrupt service routine.

At first glance, I was thinking that configuring the interrupt level and priority of the watchdog interrupt (ICR8 of INTC0) higher that the higher interrupts present on the system will to the trick of getting a watchdog system solid as a rock.  But unfortunatly, there is a case where this trick do not work at all.  When a function using critical region (all interrupts disabled), is called; if the MCU get stucked into that critical region , the watchdog system will never be able to do their job (reset the MCU).

So now, my question:  Am I missing something, or is it possible that the only way to get a solid watchdog system with that processor, is to add an external watchdog circuit?

Claude Sylvain
Electro-Technica inc.