Reset circuit in embedded systems

Hello , everyone .

I'm Shilakadeshpande , and welcome to my YouTube channel .

So today's topic is reset circuit in embedded system .

Today , we are going to see the reset circuit , what it is meant , and why it is necessary .

So let's get started without wasting much time .

Okay .

So there are some components , circuits , and ICs .

Now there are various electronic components , various circuits , and various ICs , and these are necessary for proper functioning of your controller or a processor .

For example , in our body , we have hands , we have limbs , we have nose , we have mouth , eyes , ears .

These are the organs which are necessary for proper functioning of the body .

So similarly , for the proper functioning of a controller or a processor , there are some parts which are necessary for its proper functioning .

What are the examples ?

Let's see the examples .

Examples are watch lock timer , reset IC , brown rock protection IC .

So these are the examples of the ICs and circuits which are essential for the proper functioning of the processor or the controller .

Okay ?

Fine .

And in some , controllers , they are internally connected on the com inside the compact IC .

And in some processors or controllers , they are externally connected , but they are essential for the proper functioning .

Okay .

Now we will see these parts 1 by 1 .

We will see these circuits 1 by 1 .

In today's session , we are going to cover the reset circuit .

Okay ?

Fine .

Now what is a reset circuit 2 and what do we mean by reset ?

See , in the reset , what exactly happens is , your processor or controller brings the various registers and other hardware components inside it to known state and execution starts from the vector as 0 x 4zeros , 0 , 000 , 000 .

Okay .

Means the program execution starts from the vector address 0x0000 from the beginning .

Means program starts executing from the beginning .

Okay .

So for example , if there is any circuit board and you press while the program is running or , it is in the running state or an intermediate state .

And if you press the reset button , the program execution will start from the beginning that is a firmware starts from the beginning , okay .

Again , it goes to start and from the start it executes the whole code .

So that is the reset .

Okay .

Now , there's a clock of selector and stabilization is , essential .

See , before resetting any circuit , it is very important that its block oscillator is stabilized .

Now why ?

The processor or controller works in synchronization with the clock pulses .

They work in synchronization with the clock pulses , okay .

And the reset pulse should be high enough , okay .

Because when the reset pulse is high enough , the time is given to the block oscillator circuit to stabilize .

Okay .

So reset pulse should be high .

It should be wide .

So the clock becomes it gets enough time to stabilize .

So before reset , the clock should be stabilized .

And there are 2 types of reset , active high reset and active low reset .

In active high reset , the switch is at logic high , and in the active low reset , the switch is at a logic low .

So there are 2 types of reset .

Okay .

Fine .

Now what does the reset circuit consists of ?

You can see the diagram on the right side .

There is 1 capacitor , there is 1 resistor , and there's a freewheeling diagram .

This is the diagram of the reset circuit .

External reset is essential to start the execution of a program which is , embedded in the uploaded on the processor from the beginning .

Okay .

And this is the circuit diagram of this reset circuitry .

Okay .

So it consists of the capacitor c , resistor r , and flip freewheeling diode okay and the pulse of the , reset circuit that is the active high pulse , its width .

The width of the pulse of the reset circuit can be adjusted by changing the values of the capacitance and the resistance .

If you change the value of a capacitance , if you change the value of resistance , if you adjust it in such a way that the reset pulse becomes wide enough , okay .

So , in this way we can change the width of the reset pulse by changing the value of capacitance and the resistance .

Now let's see the working .

Now what is happening ?

You can see the VCC is connected to the capacitor .

Okay .

Initially , the capacitor is charging .

You must have , known the concept of charging and discharging of the capacitor .

I would suggest that before , starting to before , reading the reset circuitry , before getting inside the working of reset circuitry , refer the working of a capacitance or capacitor in the basic electronics .

Okay .

I I'm assuming that you know the concept of charging and discharging of capacitor .

So initially by VCC , the capacitor is getting charged it's a passive component okay and when the capacitor is getting charged there is some voltage at this point .

Okay .

There is some voltage at this point and that voltage comes across this freewheeling diode .

So when the capacitor is getting charged , there is some voltage across the freewheeling diode .

A particular value of voltage nothing but the voltage of the , value of the VCC .

The voltage is developed across this freewheeling diode .

Okay .

So when the voltage is developed across the freewheeling diode , we will call it as a logic high .

And after some times , when the capacitor is fully charged , it has to get discharged .

So capacitor gets discharged through this freewheeling diode , and the resistor is there to limit the amount of a current through freewheeling diode .

So when the capacitor gets discharged across this freewheeling diode the voltage across this freewheeling diode is 0 because current is a flowing through it we will call it as a logic low .

So in this way initially voltage is at logic high then the voltage is at logic low okay .

So what is happening logic high and logic low we will get the active high pulse here .

Okay .

We will have the active high pulse here .

Okay .

Charging and discharging of capacitor according to that , the voltages are developed across the free billing diode and we get the active high pulse at the output , which is given as input to the processor to reset it .

Okay .

So this is this was the working of the , reset circuit in the embedded systems .

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