Hello, girls, and welcome back.
And this lecture, we're going to start our journey and introducing all of these electronics and embedded
systems, everything is going to start with this little bit of story, the story of the bit.
So let us get started.
I assume we have one power source, which is a battery and we have one lamp, if we connect these two
directly.
Well, this lamp will adjust light immediately as long as we have enough energy in the power source.
So this small, let's call that circuit has no control at all.
So you just, like, connect the two wires to the lab and it's going to turn on.
Nothing special here.
Now, let us look at some kind of control to this light bulb right here.
So by adding a switch right here, if we turn it on and off like that, we are going to be able to control
the Atlanta turn on that of the lamp.
So if you open the switch, the lamp will be off.
If you close the switch, the lamp is going to be on.
So this is like the most basic form of a control circuit.
It's just a small switch.
And I'm going to call this small this, which is a bit.
So if my bed is set to zero, like in this case, well, my life is going to be set to zero, meaning
gets that turned off.
And now if my switch is closed, so it is set to one, then my lab is going to be set as well to one.
Now, let us complicate this circuit a little bit.
So let us have two switches that will try to control the spot.
Now, this is a two way series switch.
I mean, why do we call it series?
Because they're both the switches right here are consecutive to each other.
So.
By closing one switch while the circuit is still open and I won't be able to light the bulb, so in
circuits there is one the rule of thumb, I need a closed circuit in order to turn on anything.
If I close both of these switches, I'm going to have a current flow and this -- right here is going
to be lit.
There is another topology of control.
Now, let us assume that I have to pull the switches, so maybe I want to control this lamp from two
different places.
So this is a different type of control.
If I turn it on from this side, well, I'm going to have a closed circuit on this path.
Right.
And the light is going to be lit.
But if I turn it on from the other side, it's going to be also lit because, well, I have another
path for the current to flow.
I can also turn both of this on.
And what's going to happen is I'm going to be able to light this bulb from both places at the same time,
unlike the series right here.
This creates some dependencies.
So switch one right here cannot be conducting unless I switch to is conducting.
Right.
So this is to be closed in order for this to close and also conduct current.
So this is the most basic form of control.
Now, let us agree on some terminology.
When we close the switch, it means that it is one.
When we open the switch, it means it's zero.
So this one and zero of the bit we are talking about now, they found out that they can do a lot of
stuff with this simple logic and they decided to call such type of switching as the end date.
It's called end because you need A and B to be on in order to conduct or get a logic at the output.
So I'm going to call these switches inputs and this is my output input is anything that I manipulate
at the input of the circuit in order to create some result at the output, which is the lab.
So this is what we call a truth table and the logic design.
So we have switch inputs, A and B, which are switches, and B, if A is zero and B is zero, as we
agreed, zero means open.
Well, the output Z is going to be zero, right.
Because, well, there is no current flowing now the same thing when A zero and B is one.
Well, same.
I'm going to get the zero because I need both of them to be closed in order to conduct anything.
So the only case that I get an output of one is one input A is one and input B is one.
If this is one and this is one, it means both are closed, then I will have an output right here.
Now, this is the end gate, we call it.
And now here we have the ogi.
It means if this switch or this switch on, I'm going to get an output right here.
So as you can see at the emptier, if A zero and B is zero, meaning both are open.
Well, of course, I don't have any current at the lamp.
Now, if I have B one meaning B is closed, well, I'm going to have a path here.
So this is going to turn out same thing when A is one and B is zero.
Also, I'm going to get the one and also when I have both of them closed, then I'm going to get an
output at the light bulb.
Right.
So we're going to start this small and we're going to build to understand how a whole microprocessor
work just by studying these small examples we're going to build up and we're going to see how will this
work see in the next lecture.