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Hello, One question about WDT feeding. The user manual is (once more) not exatcly clear about WDT refresh. It says that after writing 0xAA to WDTFEED, 'the next operation in watchdog register space should be a write 0x55 to WDTFEED', otherwise the watchdog will reset the cpu even if the timer is not yet elapsed. What happens if one interrupt triggers between 0xAA and 0x55? I see the wdt resets cpu, even if the ISR does not affect WDT register space. Do I need to disable interrupts before feeding WDT? Thank you. |
WDT feed
Started by ●February 3, 2005
Reply by ●February 3, 20052005-02-03
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As far as I know, yes. Feed sequence must not be interrupted. Kerem ----- Original Message ----- From: "extra300_it" <> To: <> Sent: Thursday, February 03, 2005 4:49 PM Subject: [lpc2000] WDT feed > > > Hello, > One question about WDT feeding. > > The user manual is (once more) not exatcly clear about WDT refresh. > It says that after writing 0xAA to WDTFEED, 'the next operation in > watchdog register space should be a write 0x55 to WDTFEED', otherwise > the watchdog will reset the cpu even if the timer is not yet elapsed. > > What happens if one interrupt triggers between 0xAA and 0x55? > > I see the wdt resets cpu, even if the ISR does not affect WDT > register space. > > Do I need to disable interrupts before feeding WDT? > > Thank you. > Yahoo! Groups Links |
Reply by ●February 3, 20052005-02-03
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At 02:49 PM 2/3/05 +0000, extra300_it wrote: >The user manual is (once more) not exatcly clear about WDT refresh. >It says that after writing 0xAA to WDTFEED, 'the next operation in >watchdog register space should be a write 0x55 to WDTFEED', otherwise >the watchdog will reset the cpu even if the timer is not yet elapsed. > >What happens if one interrupt triggers between 0xAA and 0x55? The WD feed fails. >I see the wdt resets cpu, even if the ISR does not affect WDT >register space. That's to be expected. >Do I need to disable interrupts before feeding WDT? Yes. Robert " 'Freedom' has no meaning of itself. There are always restrictions, be they legal, genetic, or physical. If you don't believe me, try to chew a radio signal. " Kelvin Throop, III |
Reply by ●February 3, 20052005-02-03
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Yes, disable ALL interrupts when writing the AA and 55 then re-enable
them. -----Original Message----- From: extra300_it [mailto:] Sent: Thursday, February 03, 2005 9:50 AM To: Subject: [lpc2000] WDT feed Hello, One question about WDT feeding. The user manual is (once more) not exatcly clear about WDT refresh. It says that after writing 0xAA to WDTFEED, 'the next operation in watchdog register space should be a write 0x55 to WDTFEED', otherwise the watchdog will reset the cpu even if the timer is not yet elapsed. What happens if one interrupt triggers between 0xAA and 0x55? I see the wdt resets cpu, even if the ISR does not affect WDT register space. Do I need to disable interrupts before feeding WDT? Thank you. ---- -- Yahoo! Groups Links a.. To |
Reply by ●February 7, 20052005-02-07
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When I first started with the LPC210x and Watchdog my board would sporadically crash - mainly then when I was dumping data to the serial port (lots of SCI interrupts). I decided to protect the feed sequence from interrupts and this cured the problem - since then the system is as solid as a rock. Therefore the feed sequence should absolutely be protected against interrupts!!! regards Mark Butcher www.mjbc.ch --- In , "extra300_it" <roberto.labaa@l...> wrote: > > Hello, > One question about WDT feeding. > > The user manual is (once more) not exatcly clear about WDT refresh. > It says that after writing 0xAA to WDTFEED, 'the next operation in > watchdog register space should be a write 0x55 to WDTFEED', otherwise > the watchdog will reset the cpu even if the timer is not yet elapsed. > > What happens if one interrupt triggers between 0xAA and 0x55? > > I see the wdt resets cpu, even if the ISR does not affect WDT > register space. > > Do I need to disable interrupts before feeding WDT? > > Thank you. |
