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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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