Watchdog in AT89S8252 ?!?

[mrcube_ns]

I need to use watchdog in AT89s8252 (I new in atmel programming).

How to do it?

Some code examples are welcome.

THANKS IN ADVANCE.

Mr.Cube

 

[Eskimo]

Sample code

//Refresh macro
#define REFRESH_WATCHDOG() WMCON = WMCON | 0x02

void main()
{
// Init WatchDog
WMCON = WMCON | 0xE0; /* TimeOut Period = 2048ms */
WMCON = WMCON | 0x01; /* Enable WatchDog*/

while (1)
{
//Refreshing
REFRESH_WATCHDOG();
}
}

 

[C-Man]

A little tip: do not refresh your watchdog inside an interrupt routine because most of the time interrupts are still running while your main routine has crashed for some obscure reason

Better refresh your watchdog inside a routine which is not called too often or set some flags inside a few routines and only refresh your watchdog (and reset the flags) when all flags are set (this can be done inside your interrupt routine), works much better for me ...

best regards

 

[mrcube_ns]

If I understand well you must refresh wd every 2 sec (max), on which xtal?

Mr.Cube

PS. C-man don't you afraid that your uC will restart if some of those flags aren't set ('couse of some conditions or input states)?

 

[Eskimo]

WD operates from an independent oscillator.
Look at datasheet page 9.
http://www.atmel.com/dyn/resources/prod_documents/doc0401.pdf.
Refresh must be faster then slected period.