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A strange situation where an internal watchdog reset implementation seems not to work on the 87c520 target while it does work ok when using the Ceibo ICE. Seems like the reset occurs but unclear where the PC jumps to because the SW does not restart properly but rather stays "stuck" (we know it enters the if (status) passage). With the ICE the program does start ok. What we do is enable the watchdog timer in the program. In the interrupt handler (ISR 12) depending on some status, we enable the reset itself. All this occurs, but then for the target the program does not go into running normally. Any ideas? Thanks, Baruch if ( status ) // { TA = 0xAA ; //Accessing timed access in order to start the watchdog timer TA = 0x55 ; // EWT = 1 ; // Enable WatchDog timer reset TA = 0xAA; //Accessing timed access in order to start the watchdog timer TA = 0x55; // WDIF = 0 ; // watch dog flag clear } else { TA = 0xAA; //Accessing timed access in order to start the watchdog timer TA = 0x55; // WDIF = 0 ; // watch dog flag clear TA = 0xAA ; //Accessing timed access in order to start the watchdog timer TA = 0x55 ; // RWT = 1 ; // Restart Watchdog timer }
void main () { // disable WDT hardware reset. // if wdt ever fires, // the initialization // and the prom checksum could not // complete before wdt fired again, // staying there forever, so disable // wdt till checksum over. // disable WDT hardware reset EA = 0; // disable all interrupts TA = 0xaa; TA = 0x55; WDCON = WDCON & ~EWT_; other initialization here then just before main loop // initialize WATCH Dog Timer // set WDT for 56.889MS...18.432mhz cry // see page 116 in dallasbook CKCON |= WD0_; CKCON &= ~WD1_; // Enable hardware reset // if Watch Dog Timer expires EA = 0; // disable interrupts TA = 0xaa; TA = 0x55; WDCON = WDCON | EWT_; // Enable WDT EA = 1; // enable interrupts // MAIN LOOP do { //Watch Dog Timer Reset EA = 0; // disable interrupts !! // if any interrupt occurs during // the following 3 instructions // the wdt will not be reset // so disable interrupts TA = 0xaa; TA = 0x55; WDCON = WDCON | RWT_; //reset wdt EA = 1; // enable all interrupts!! other main loop things }while(1); } // end of main