What is the actual application scenarios of the external watchdog module

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What is the actual application scenarios of the external watchdog module

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945595199
Contributor I

I am using EWM module in S32K146,and have some question about EWM's application scenarios:

1. Why EWM_out can be de-assert only by forcing system reset?I am confused about what application scenarios need to be so extreme,have a specific example?Can I release EWM_out pin by reset EWM module,because I want to de-assert EWM_out pin by my software setting but not reset system. 

2. If EWM_in is enable,the EWM_in looks like must input the same frequency square wave as the software refresh EWM frequency and EWM_in should de-assert when feed dog to avoid assert EWM_out. The picture below shows:

EWM.png

 However,the EWM module clock source is LPO,so the EWM_in's clock source also should be it,otherwise, if LPO clock and EWM_in's clock is asynchronous,the EWM_out will assert in the future.

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danielmartynek
NXP TechSupport
NXP TechSupport

Hi,

1.
The EWM_out pin is used to place an external circuit into a safe mode.
It is a safety feature, the CTRL_EWMEN deaserts the EWM_OUT_b signal, but this bit is a write-once bit and therefore system reset is required to re-enable the EWM module.

2.
The EWM_in input allows an external circuit to control the assertion of the EWM_out signal.
If there is a fault in the external circuit, the EWM_in is asserted, otherwise it is deaserted.

danielmartynek_1-1605024444396.png

 

Regards,

Daniel

 

 

 

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