Part Number: TMS320F28065
Hi Support,
my customer had some alarms in the safety check of watchdog (WD) on a TMS320F28065 device.
They happened at low temperatures. After checking the Datasheet I found that the internal oscillator (on which the WD is clocked) has a significant drift with temperature and this was the cause of the "fails" of the tests. The safety libraries (Soprano ones) are considering timing coefficients that customer took as reference. Of course the issues they are facing suggest that these parameters need to be tuned on the actual drift of the oscillators. Could you confirm the tolerances and the precision of the uC internal oscillator is the one reported at paragraph 5.13 (in particular table 5-7 and Figure 5-8) of the device datasheet?
At present the WD test, performing OK at room temperature, are failing as soon as the ambient temperature falls below approx. 15°C (average of multiple samples). The coefficients used are referenced in the following points of the safety library code.
1) The wait-dalay passed as parameter in the call:
STL_WATCHDOG_TEST_testWatchdog(STL_U_WDOG_TEST_TIMER_VAL)
2) The accepted oscillator drift (MAXIMUM_WATCHDOG_DELAY_DRIFT) considered in the check:
if(gWatchDogDelay > MAXIMUM_WATCHDOG_DELAY_DRIFT){ ... }
inside the function:
interrupt void STL_WATCHDOG_TEST_watchdogIsr(void)
Customer has to fine-tune them according to the expected working temperature range and supply voltages.
Thanks and regards,
Alberto
