Welcome to electrical and electronics engineering Q&A site...

Welcome to electrical and electronics engineering discussion website, Please login or register to continue.

Join our WhatsApp group

Subscribe To Our YouTube Channel

196 views
in Unit 2 by
What is watchdog timer ? Explain the implementation of time out for ATM with block diagram and program.

Amazon Shopping

Please log in or register to answer this question.

1 Answer

0 votes
by

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.

image

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.

image

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.

Amazon Shopping

Welcome to Q&A site for electrical and electronics engineering discussion for diploma, B.E./B.Tech, M.E./M.Tech, & PhD study.
If you have a new question please ask in English.
If you want to help this community answer these questions.

Categories

Most popular tags

power motor dc circuit transformer voltage current used system phase factor resistance load synchronous energy ac induction generator electric series frequency capacitor use speed between electrical meter line type mosfet control transmission difference magnetic plant high single instrument bjt source advantages function diode machine unit winding torque amplifier define supply thyristor motors arduino field shunt maximum relay armature problem electricity time parallel on transformers types coil diagram state flow value material three starting and direction theorem method emf operating digital microprocessor test instruments efficiency ratio loss measure operation connected low applications wave effect single-phase working losses different network wattmeter temperature measuring constant signal controlled breaker device full compare drive wire resistivity logic materials machines inductance switch flux disadvantages converter transistor gain protection scr angle force core measurement number free principle rc generators law negative bridge friction open pole conductor conservation steam iron loop resistors hysteresis short computer using lines secondary station battery rectifier inverter linear relays nuclear regulation circuits design analog work rotor electronics gate forces diesel damping rlc connection factors capacitors minimum insulation basic moving running reactance systems air fault range direct main stability quality starter igbt eddy ideal ammeter rl 3-phase plants arc induced thermal error fuzzy biasing dielectric pressure balanced superposition errors rotation characteristics feedback measured electronic start alternator off back curve over solar three-phase tariff locomotive peak bias zener capacitance commutator surge rating universal potentiometer permanent mechanical copper self transducer capacity electrons memory adc excitation inductive transfer explain fuse pure harmonics application inductor internal pmmc average reaction welding resonance traction breakers designed electromagnetic si generation brushes density switching shaded rate impedance distribution methods star oscillator reluctance semiconductor simplification algebra 8085 boolean weston dynamometer insulating strength installation permeability definition fuel heating earth units neutral rms rated engineering conductors coefficient controller usually reverse excited analysis change body components
...