What is watchdog timer ? Explain the implementation of time out for ATM with block diagram and program.

1 Answer

A special type of timer is a watchdog timer, which will reset the system after a predefined timeout. Watchdog timer reset timer every X time unit, else timer generates a signal indicating that the system failed. A common use of watchdog timer is to enable an embedded system to restart itself in case of a failure.
Another common use is to support timeouts in a program while keeping the program structure simple.


Example of ATM timeout using a watchdog timer:-
In this example, a watchdog timer is used to implement a timer out for an automatic teller machine (ATM).
A normal ATM session introduces a user inserting a bank card, typing in a personal identification number (PIN), and then answering questions about whether to deposit or withdraw money, which account will be involved how much money will be involved, whether another transaction is desired and so on.
We want to design the ATM such that it will terminate the session if at any time the user does not press any button for a minute. In this case, the ATM will eject the bank card and terminate the session.


As oscillator signal, OSC is connected to prescaler that divides the oscillator frequency by 12 (OSC/12) to generate a signal clk.
The signal clock is connected to an 11-bit up counter scalereg. When scalereg overflows, it rolls over to "o", and its overflow output causes the 16-bit up counter timer reg to increment.
If timing overflows, it triggers the system reset or an interrupt. To reset the watchdog timer, checkreg must be enabled. Then a value can be loaded into timereg.
When a value is loaded into timereg, the checkreg register is automatically reset. If the checkreg register is not enabled. a value can not be loaded into timereg. This is to prevent erroneous software from unintentionally resetting the watchdog timer.

Like 0 like Dislike 0 dislike

Related questions

Description : What is the difference between a counter and a timer?

Answer : Counter counts only when the trigger is applied and timer counts continuously with some equal delay.

Description : What is the use of 555 timer?

Answer : 555 IC timer is use in timers and oscillators.

Description : Blackt Electrotech 230V 24x7 Energy Saving Socket Type Digital Programmable Plastic Electronic Timer (White)

Answer : Buy from amazon: https://amzn.to/2SUTSdv Buy: http://bit.ly/2ZqlAkS

Description : Why is it called a 555 timer?

Answer : Because it have three 5k Ohm resistances.

Description : Explain with neat sketch block diagram of optical fiber communication system and list out sources and detectors suitable for it.

Answer : OR 1. The light source is normally an infrared LED or LASER device which is driven by the current value from the V to I convertor. It emits light which is proportional ... optical energy electrical signal. The light detectors which are used as PIN photodiode and avalanche photo diode.

Description : Employee recognition can: (a) Be a strong motivator. ; (b) Lead to unrealistic expectations. ; (c) Help with MBO program implementation. ; (d) Assist with goal setting.

Answer : (a) Be a strong motivator. ; 

Answer : A design metric is a measure of a implementations features such as cost, size, performance and power.Commonly used design metrics are:1.NRE cost:NRE stands for non recurring engineering cost. ... to check that manufacturing was correct.11.Safety:The probability that the system will not cause harm.

Description : List & explain the timer instruction of PLC. Draw the ladder diagram to verify (i) OR gate& (ii) NOR gate logic 

Answer : Depending on the time delay and operation, there are two types of timers  * PLC timer- (i) ON delay timer  (ii) OFF delay timer Description (i) ON delay timer 1) This instruction counts time interval when ... a) OR gate ladder diagram y = A + B b)NOR gate ladder diagram

Description : Explain memory write ability and storage permanence with suitable diagram.

Answer : Write ability and storage permanence of memories: Write ability is the manner and speed at which memory can be written. Storage permanence is the ability of memory to hold stored bits ... Holds bits after power is no longer supplied. High end and middle range of storage permanence.

Description : Draw block diagram of Dual slope integrating voltmeter and also draw waveform for voltage V/s time. 

Answer : Block diagram

Description : Consider an implementation of unsorted single linked list. Suppose it has its representation with a head and a tail pointer (i.e. pointers to the first and last nodes of the linked list). Given the ... the front node of the linked list. (D) Deletion of the last node of the linked list.

Answer : (D) Deletion of the last node of the linked list. 

Description : What is EGR? Explain with the help of block diagram.

Answer : Exhaust Gas Recirculation Valve (Operation-2 marks, Sketch-2 marks) When the engine is idling, the EGR valve is closed and there is no EGR flow into the manifold. The EGR valve remains closed until the ... exhaust gas (less than 10% of total) to be supplied into the incoming air: fuel mixture

Description : What is PLL? Explain its operation with a block diagram.

Answer : PLL - A phase-locked loop or phase lock loop is a control system that generates an output signal whose phase is related to the phase of an input signal Block diagram  ... to the input frequency. The phase - locked loop goes through three states free running capture and phase lock.

Description : What is ‘MEMS’? Explain with neat block diagram.

Answer : Definition of MEMS: MEMs are Mechatronics systems that consist of mechanical elements and electronic circuits. A micro electromechanical system is an integration of mechanical elements, sensors, ... actuators and signal transduction unit, closed loop control system can be easily developed.

Description : Explain the working of MTI radar with the help of block diagram and with suitable waveforms.

Answer : Explanation : The echo pulse from the target is received by MTI radar antenna. If echo is due to moving target, the echo pulse undergoes a Doppler frequency. The received echo pulses then pass ... for fixed target magnitude and polarity of output will remain the same as shown in figure.

Description : Draw the block diagram of PCM receiver with the help of relevant wave form and explain its working

Answer : Block diagram of PCM receiver:- Explanation:- A PCM signal contaminated with noise is available at the receive input. The regeneration circuit at the receiver will separate PCM pulses from noise ... quantized PAM signal is passed through a low pass filter recovers the analog signal x (t).

Description : Explain the Mechatronics system with the help of block diagram and labeled the various elements. 

Answer : The key elements of Mechatronics systems can be classified under following categories:  Information systems  Mechanical systems  Electrical systems  Computer systems  Sensor and actuators  ... is adjusted based on generated error and again signal is given to actuators and sensors.

Description : Draw block diagram of digital frequency meter in time mode and describe its operation.

Answer : OR Operation: The input signal is amplified and converted to a square wave by a Schmitt Trigger circuit. In this diagram the square wave is differentiated and clipped to ... thereby closing it. The decimal counter and display unit output correspond to the number of input pulses. 

Description : State what is the significance of conducting phasing out test on a 3-phase transformer? Explain its procedure with a suitable connection diagram.

Answer : -Short primary & secondary winding of other phases expect the one under test. -Connect voltmeter to secondary winding. -A small DC current is circulated through the primary winding through ... . -The test repeated for finding out remaining concerned secondary windings in the same manner.

Description : Draw block diagram for CNC drilling machine and explain its working.

Answer : Block diagram consist of the following points:  Machine tool with DC servo motor as feedback element. The transducer is added as adaptive control application.  The auxiliary controller ... line.  The interrupt pulses are generated by TBG and supplied to computer through inter

Description : Draw the block diagram for PLC power supply and explain the function of each block.

Answer : PLC power supply generates the required dc voltage levels for operation of the internal circuit of PLC. It is a switched mode power supply which accepts wide range of AC/ DC input ... of power failure from AC input, Battery backup becomes active and prevents accidental shut down of PLC

Description : Explain with block diagram working of microprocessor controlled ignition system.

Answer : The microprocessor controlled ignition system uses input from sensors like crankshaft position sensor, oil temperature sensor, ignition trigger coil and throttle position sensor. The ignition module/ ... the ignition module / microprocessor enables the spark to be timed accurately.  

Description : Explain the concept of single beam dual trace CRO with its block diagram.

Answer : Diagram:   Explanation: The single beam dual trace CRO consists of one electron gun, an electronic switch which switches the two signals to a single vertical amplifier and a single pair of ... Amplifier are identical & have the same delay time, accurate X-Y measurements can be taken. 

Description : Explain function of each block of logic analyzer with proper block diagram

Answer : Explanation: A logic analyser is an electronic instrument that captures and displays multiple signals from a digital system or digital circuit. The normal oscilloscope deals with time domain, spectrum ... When the memory receives a trigger signal, it sends the samples to a CRT display.  

Description : Explain working of LPG kit with labeled block diagram.

Answer : Working of LPG Kit: LPG Tank: It is used to store the LPG at 10 bar Filler Valve: It allows the LPG into the tank while feeling. Pressure Relief Valve: It is used to limit ... regulator Mixer / gas injection which flows the LPG into the combustion chamber  Block diagram:  

Description : With the help of block diagram explain closed loop control CNC system. 

Answer : Special motors called servos are used for executing machine movements in closed loop system. The name indicates that the closed loop control system has a loop that is closed as shown in fig. ... to the drive unit and the cycle repeats until there is no error signal from the comparator.

Description : Explain with block diagram of Armstrong method of FM generation.

Answer : Explanation:- The crystal oscillator generates the carrier at low frequency typically at 1 MHz this is applied to the combining network and a 90o phase shifter. The modulating signal is passed through an ... power amplifier to raise the power level of the FM signal.  Phasor Diagram:-   

Description : Explain with block diagram the working of programmable logic control system. (PLC).

Answer : Programmable logic controller:  Block diagram: OR Explanation: PLCs are industrially hardened microcomputers that perform discrete or continuous control functions in a variety ... provides an interface between the PLC and user during program development, start-up and trouble shooting

Description : Explain with the help of block diagram, spread spectrum modulation system.

Answer : SPREAD-SPECTRUM COMUNICATION SYSTEM  Baseband DS spread spectrum communication system model (a)transmitter (b) channel (c)receiver Explanation:- In actual DSSS system, the ... PN sequence pattern which the receiver will recognize in the presence of interference with high probability.

Description : Explain digital communication system with the help of block diagram.

Answer : Block diagram of digital communication system:- Explanation:- DISCRETE INFORMATION SOURCE: The information to be transmitted originates here. These information/messages may be available in digital ... its output, a replica of the output of the digital source at the transmitting end. 

Description : Explain direct sequence spread spectrum (DSSS) transmitter with block diagram.

Answer : In direct sequence, the serial binary data is mixed with a higher frequency pseudorandom binary code at a faster rate and the result is used to phase-modulate a carrier. The ... 1010 with odd parity. le of spread spectrum modulation and demodulation using PSK for primary modulation.

Description : Explain DPCM with block diagram.

Answer : The above figure shows the block diagram of DPCM transmitter x(t) is the analog input signal and x^(t) is its approximated signal. What is important to know is whether x^(t) ... used to produce the approximated signal x^(t)by passing the quantizer output through a predictor and accumulator.

Description : Explain microcontroller based antilock brake system with neat block diagram.

Answer : An ABS is a system on motor vehicles which prevents the wheels from locking while braking stopping safely is one of the most important functions a motor vehicle can perform ... valves to decrease the pressure on the braking circuit, effectively reducing the braking force on that wheel.

Description : Explain the operation of UPS with a neat block diagram.

Answer : Uninterruptible-Power-Supplies (UPS): A block diagram of UPS system is shown in figure. It essentially consists of four major components: i)Rectifier (or battery charger) ii) ... . Due to fast action requirement, transfer switch can be implemented by fast acting semiconductor devices.

Description : Explain operation of µP based relay with block diagram

Answer : Operation of Microprocessor (µP) based relay: The inputs from the power system through CTs and PTS are received by the analog Input receiver; they are sampled simultaneously or ... compares the dynamic inputs and decides accordingly to generate trip/alarm signal to the output device.

Description : Explain with block diagram photovoltaic power generation.

Answer : Photovoltaic power generation:  Photovoltaic power generating system consists of following components: 1. Photovoltaic cell panel: Its function is to convert energy content of sunrays directly into DC ... . Step-up transformer: It step-up input voltage to utilization voltage e.g. 230V.

Description : Consider a disk queue with request for input/output to block on cylinders  98, 183, 37, 122, 14, 124, 65, 67  in that order. Assume that disk head is initially positioned at cylinder 53 and moving ... and 252 cylinders (B) 640 and 236 cylinders (C) 235 and 640 cylinders (D) 235 and 252 cylinders

Answer : Answer: 236 and 208 cylinders Explanation: SSTF Initial head position =53 The closest queue to initial head position=65 head moves from 53 to 65=12 head moves from 65 to 67=2 head moves from 67 ... 122=24 head moves from 122 to 124=2 head moves from 124 to 183=59 Total head movement=208 

Description : Consider a disk with 16384 bytes per track having a rotation time of 16 msec and average seek time of 40 msec. What is the time in msec to read a block of 1024 bytes from this disk? (A) 57 msec (B) 49 msec (C) 48 msec (D) 17 msec

Answer : Answer: B

Description : Draw block diagram of distortion factor meter and explain its operation.

Answer : Block Diagram Operation This meter consist following four sections 1. Impedance converter along with input circuit 2. Rejection amplifier 3. Metering circuit 4. Power circuit 1. ... of the total input voltage. 4. The power supply unit provides the supply for proper operation 

Description : Draw block diagram of RF signal generator and explain its operation.

Answer : RF signal generator contains three other main sections: 1.OSCILLATOR CIRCUIT, 2. MODULATOR, 3. OUTPUT CONTROL CIRCUIT. The modulator modulates the RF signal of the ... . Metal shielding surrounds the unit to prevent signals from the oscillator from affecting the circuit under test

Description : Draw and explain block diagram of Horizontal deflection system. 

Answer :  Trigger circuit: A trigger circuit is used to convert the incoming signal into trigger pulses, so that the input signal and the sweep frequency can be synchronized. The trigger circuit is ... before it is applied to the horizontal section. The block consists of a push- pull amplifier  

Description : Draw block diagram of digital LCR –Q meter and explain its working.

Answer : Block diagram Working The output of LCR-Q meter is given to current to voltage converter, AC amplifier or DC amplifer depending upon position of switch Current to voltage ... /D converter. A/D converter converts analog signal into digital output andfinaaly displayed on display.

Description : Explain block diagram of distortion factor meter and explain how it operates

Answer : Fig. Distortion factor meter  Working : Initially the switch S is kept at position 1. The attenuator gets excluded and the bridge T network is adjusted for full suppression of ... is obtained on the meter. Thus the total rms distortion is indicated by the reading of attenuator.

Description : Describe block diagram of spectrum analyzer and explain its working

Answer : Fig: Block Diagram of Spectrum analyzer. 1. Spectrum analyzer consists of voltage tune oscillator, mixer, IF amplifier, detector, video amplifier, sweep generator and CRT. 2. The input ... on the screen. 8. In this type the signal are broken down into their individual frequency component.

Description : Draw block diagram of AF sine and square wave generator and explain its working

Answer : The AF signal generator, which generates either sine wave or square wave in the range of audio frequencies based on the requirement is called AF Sine and Square wave generator. Its block diagram is shown ... can be used to produce either AF sine wave or AF square wave based on the requirement. 

Description : Draw and explain the block diagram of fuzzy logic controller.

Answer : Ans:  OR 1 Fuzzification: It is the action of transforming a given state as crisp input into fuzzy values by evaluating membership function for purpose to be used by a ... at producing a non- fuzzy control action that best represent the possibility of an inferred fuzzy control action

Description : Draw block diagram of FM receiver and explain the use of limiter circuit.

Answer : Diagram Explanation Amplitude limiter: The function of amplitude limiter is to remove all amplitude variation of FM carrier voltage that may occur due to atmospheric disturbances. Use of amplitude limiter makes the system less noisy.

Description : Draw and explain block diagram of electronic communication system.

Answer : Block diagram of electronic communication system. Explanation Transducer: A transducer is usually required to convert the output of a source into an electrical signal that is suitable for ... etc. Output Transducer: The output transducer converts electrical signal in to sound signal.  

Description : Draw the TRF receiver block diagram and explain its working. 

Answer : Explanation:- 1. TRF receivers are simple and having high sensitivity. The AM transmission takes place in MW band and SW band. MW frequency range is 540KHz to 1640KHz. 2. ... power level to drive the loudspeaker. 7. The loudspeaker converts electrical signal into original sound information.

← Prev Question Next Question →
Ask a Question
Choose topic