Jaroslav Lepka

KV3x -  watchdog issue

Discussion created by Jaroslav Lepka on Aug 11, 2016
Latest reply on Aug 11, 2016 by Chris Brown
This message was posted by Christopher Brown on behalf of Jaroslav Lepka via Jive for Outlook

Hi Chris,


Sorry to bother you, but I would like to ask you for help with watchdog behavior on KV3x devices.

Customer would like to use watchdog on KV3x and observed issue with integrating it into his application.



-          Watchdog clock source: LPO at 1 kHz. It is necessary to have independent clock for watchdog which must be different from core clock

-          Timeout value: 10 s (register value - 10000 at 1 kHz)

-          Window value: 0

-          Prescaler value: 0

-          Watchdog is refreshed periodically in the interrupt triggered by SysTick (IsrSysTick interrupt handler) every 1 ms



a)       The watchdog is not refreshed with the period of 1 ms

b)      How to refresh watchdog during the startup code when it is difficult to keep period larger than 1 ms? Will the watchdog be updated correctly even if the update will happen several times in 1 ms period?



1)      The issue is probably caused by watchdog input clock which is 1 kHz (1 ms)

2)      Is it possible to update watchdog anytime regardless of watchdog source clock which means more often than just once in 1 ms period? If so, how does this work?

3)      Since it is synchronous design the watchdog peripheral module is probably triggered with 1 kHz clock.

4)      How can we manage watchdog update in startup code? It is difficult to keep 1 ms time frame. It is changing with startup code complexity and it is application dependent



Thanks for your help




Best regards


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Jaroslav Lepka

Principal Engineer, Motor Control & Safety Team Leader

Security & Connectivity, Microcontrollers

NXP Semiconductors

1. maje 1009

75661 Rožnov pod Radhoštěm

Czech Republic

Phone: +420 571 665 132

Cell:     +420 604 291 188

Email: jaroslav.lepka@nxp.com