LPC WWDT

[lpcware]

Content originally posted in LPCWare by sticwin on Mon Jun 09 01:28:37 MST 2014
when configued WWDT as below:

LPC_WWDT->TC = 4689;
LPC_WWDT->WARNINT=200;

i suppose to let WWDT reset the MCU when time is out, but when "WARNINT" is less than 255, the WWDT won't reset the MCU, i wonder why??

[lpcware]

Content originally posted in LPCWare by NXPARM on Mon Jun 09 19:03:17 MST 2014

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Quote: arw
Hello,

This is related to the minimum value of TC, being 0xFF.  A valid setting of the warning interrupt should be greater than the minimum value of the TC.  Use values above 0xFF for the warning interrupt level.

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i have one more question, when applys WWDT during power down mode, which uses WWDT warn interrupt to wakeup the MCU. In this condition, i fed the WWDT after MCU wakeuped immediate, the MCU will instantly reseted, but if i add a delay about 1ms then the feeding won't has any problem. this situation will only happen when protect bit in MOD(bit 4) is setted.

   As for WWDT the TC, it is used to load the value to the WWDT timer when feed sequence is happened. this mean the TC is definitely not the same conception of WDT timer. So i really doubt what the user manual indicated that the protect bit is only used to protect the TC from being unwanted changed. but my application has never changed TC except initialisation. Why the protect has so much effect with WWDT.

[lpcware]

Content originally posted in LPCWare by NXPARM on Mon Jun 09 18:47:06 MST 2014

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Quote: arw
Hello,

This is related to the minimum value of TC, being 0xFF.  A valid setting of the warning interrupt should be greater than the minimum value of the TC.  Use values above 0xFF for the warning interrupt level.

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but when i disable the bit 4 in the WWDT MOD register every thing is OK, whether for WWDT reset or WWDT warm interrupt. And there is no description in the lpc812's user manual show that the WWDT WARNINT shouldn't small than 0xFF. it just indicate the TC as that way.

[lpcware]

Content originally posted in LPCWare by arw on Mon Jun 09 10:21:35 MST 2014
Hello,

This is related to the minimum value of TC, being 0xFF.  A valid setting of the warning interrupt should be greater than the minimum value of the TC.  Use values above 0xFF for the warning interrupt level.