...function of a watch dog timer?

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Answer by zap
Submitted on 4/25/2005
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Software stability is a major issue on any platform. Anyone who uses software has probably experienced problems that crash the computer or program in question. This is also true of embedded programs, and in most cases there is no user around to reset the computer when things go wrong. That job is occupied by the watchdog timer. The watchdog timer is a 16 bit counter that resets the processor when it rolls over to zero. The processor can reset the counter or turn it off, but, correctly used, it will reset the processor in case of a code crash. To avoid getting reset, the program must reset the timer every so often. A program which has crashed will not do so, and the system will reset. To improve its efficacy, the watchdog timer register also requires a password. In order to change the lower part of the watchdog control register, the upper part of the register must be written with a specific value. This value is specified by the alias WDTPW in the MSP header files. This password reduces the likelihood that a random crashed instruction could prevent the reset. In situations where a system crash is not a concern, the watchdog timer can also act as an additional timer. The watchdog timer can be configured to give an interrupt when it rolls over; this interrupt could also be used to handle system crashes. While the watchdog timer is not as versatile as the other MSP430 timers, the watchdog control register WDTCTL still allows selection of the timer’s divider and clock source. Often the watchdog timer is simply turned off by setting the hold bit in the control register. Any changes to this register require writing the password to the upper bits.

Answer by prank
Submitted on 10/20/2005
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Main feature is to ensure that software runs smoothly and system does not get hang. The software service method and service interval for the timer varies from processor to processor. The software system is responsible for servicing the watchdog at the interval to keep the system alive. But if the software fails to service the watchdog for a span of time greater than the service interval, hardware circuits will reset the processor. Triggering a reset implies the system is unreliable: in an unknown state, caught in a loop with interrupts masked, or busy handling a barrage of constant interrupts. As a last resort to handle an unpredictable situation, the processor resets the software system using the watchdog timer mechanism.

Answer by Ari Narayanan
Submitted on 1/20/2006
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Software stability is a major issue on any platform. Anyone who uses software has probably experienced problems that crash the computer or program in question. This is also true of embedded programs, and in most cases there is no user around to reset the computer when things go wrong. That job is occupied by the watchdog timer. The watchdog timer is a 16 bit counter that resets the processor when it rolls over to zero. The processor can reset the counter or turn it off, but, correctly used, it will reset the processor in case of a code crash. To avoid getting reset, the program must reset the timer every so often. A program which has crashed will not do so, and the system will reset.

Answer by ganesh.v.r
Submitted on 5/18/2006
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A watchdog timer (WDT) is a device or electronic card that performs a specific operation after a certain period of time if something goes wrong with an electronic system and the system does not recover on its own. A common problem is for a machine or operating system to lock up if two parts or programs conflict, or, in an operating system, if memory management trouble occurs. In some cases, the system will eventually recover on its own, but this may take an unknown and perhaps extended length of time. A watchdog timer can be programmed to perform a warm boot (restarting the system) after a certain number of seconds during which a program or computer fails to respond following the most recent mouse click or keyboard action. The timer can also be used for other purposes, for example, to actuate the refresh (or reload) button in a Web browser if a Web site does not fully load after a certain length of time following the entry of a Uniform Resource Locator (URL). A WDT contains a digital counter that counts down to zero at a constant speed from a preset number. The counter speed is kept constant by a clock circuit. If the counter reaches zero before the computer recovers, a signal is sent to designated circuits to perform the desired action.

Answer by MANOJKUMAR T
Submitted on 12/19/2006
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A watchdog timer (WDT) is a device or electronic card that performs a specific operation after a certain period of time if something goes wrong with an electronic system and the system does not recover on its own. A common problem is for a machine or operating system to lock up if two parts or programs conflict, or, in an operating system, if memory management trouble occurs. In some cases, the system will eventually recover on its own, but this may take an unknown and perhaps extended length of time. A watchdog timer can be programmed to perform a warm boot (restarting the system) after a certain number of seconds during which a program or computer fails to respond following the most recent mouse click or keyboard action. The timer can also be used for other purposes, for example, to actuate the refresh (or reload) button in a Web browser if a Web site does not fully load after a certain length of time following the entry of a Uniform Resource Locator (URL). A WDT contains a digital counter that counts down to zero at a constant speed from a preset number. The counter speed is kept constant by a clock circuit. If the counter reaches zero before the computer recovers, a signal is sent to designated circuits to perform the desired action

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Question by nachi
Submitted on 10/9/2003
Related FAQ: comp.sys.ibm.pc.hardware.* Frequently Asked Questions (FAQ) Part 1/5
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what is the function of a watch dog timer?

Answer by hungvt
Submitted on 11/18/2003
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Watch dog timer is a robust timer. It is independent with existence the whole system. If there is a problem with system, reset makes decision based on pulses from system to reset the system and reset the system. It make our systems more reliable. You can see its usefulness in industrial networks.

Answer by mohsen kowkabi
Submitted on 2/7/2004
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watch dog timer is a benefit reset for your system.when it is hanging or cant be able to work correctly.

Answer by laxel
Submitted on 4/17/2004
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if the watchdog isn`t enable. whats up?

Answer by rakesh kumar giri
Submitted on 11/18/2004
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if watch dog timer is not exiting ,our system will be remain unsafe.as the name ,it guides us.

Answer by ramya
Submitted on 5/4/2005
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it is a timer which resets the machine with the specified time in the routine. Initially it needs to be cleared, manually.

Answer by prash
Submitted on 5/10/2005
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vmvmbmnv

Answer by jam
Submitted on 8/10/2005
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watchdog timer is used to stop system to do malfunctioning.In embedded system it is better to reset the system rather than allowing it to do malfunctioning

Answer by Kurt
Submitted on 1/3/2006
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if the watchdog isn`t enable. whats up? >>if you overclock your system , then when your system unstable and halt by overclock, system would not be reset and recover the save value. And you have to open your case to clear the CMOS,that would be so bother.

Answer by Shobana.S
Submitted on 1/24/2007
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It is a timer loaded with the value as required for the application .if the system is working properly the timer will never reach zero since it will be reloaded .If the system fails due to code hang or any software problem the timer flows to zero causing the processor to reset.thus the watchdog timer.

Answer by Jeyaseelan
Submitted on 2/12/2007
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Most Embedded system have no resetting the processor. To facilitate the processor resetting, a watchdog timer is used. This timer is set to a large value and is counted down. When the value reaches zero, the processor is reset. If everything is going fine and there is no need to reset the processor, the processor reset the watchdog timer (by kicking the timer0 to a large value again. This procedure takes care of undiscovered bugs in software.

Answer by seenu
Submitted on 4/24/2007
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Watch dog timer is a robust timer. It is independent with existence the whole system. If there is a problem with system, reset makes decision based on pulses from system to reset the system and reset the system. It make our systems more reliable. You can see its usefulness in industrial networks

Answer by juan bibo
Submitted on 6/20/2007
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watch dog timer, by the words alone, it already gives you an idea of what its definition. A watch dog timer is a dog that watches the clock....idiot!!!!

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