RE: Can WDT reset be postponed?

flopash — Mon, 23 Apr 2018 21:57:58 GMT

I wanted to follow up with this. I looked into the documentation and for the nRF52832, the time to write one 32-bit word appears to be a minimum of 67.5 us (https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v14.0.0%2Fmigration.html).

This would not have enough time to complete the write before the watchdog reset. Is this accurate, or am I missing something else?

RE: Can WDT reset be postponed?

Susheel Nuguru — Wed, 11 Apr 2018 02:02:40 GMT

Two things

1) Giving any ability to postpone reset (more than what is allowed) after WDT timeout will fail the purpose of the watchdog.

2) It is not two cycles of 32MHz but two clock cycles of 32KHz

Watchdog reset

A TIMEOUT event will automatically lead to a watchdog reset.

See Reset for more information about reset sources. If the watchdog is configured to generate an interrupt on the TIMEOUT event, the watchdog reset will be postponed with two 32.768 kHz clock cycles after the TIMEOUT event has been generated. Once the TIMEOUT event has been generated, the impending watchdog reset will always be effectuated.

That should give you enough time to write one word to flash as it takes about 40uS to do so.

t_WRITE

Time to write one 32-bit word

41¹

µs