Hello.
Welcome back.
In this lesson we shall give a brief overview of the universal asynchronous receiver transmitter otherwise
known as the U art computers transfer data in two ways parallel and serial in parallel data transfers
often eight or more lines or wires are used to transfer data to another device in serial communication.
The data is sent one bit at a time in the past.
Parallel data transfer was preferred for short distances because it's made transfer multiple bits at
the same time and provide higher throughput.
As technology advances the data rate of serial communications sometimes exceed parallel communication
while parallel communication still retains the disadvantages of the size and cost of cable and connector.
The crosstalk between the data lies and the difficulty of synchronizing the arrival time of data lies.
Longer distances also still existed in the parallel communication you.
Art is one of the most common serial communication protocols and in this lesson we shall explore some
of the basics of the new art protocol the data coming in at the receiving end of the data line in a
serial data transfer.
Is all zeros and ones.
It is difficult to make sense of the data unless the sender and receiver agree on a set of rules or
a protocol on how the data is packed.
How many bits constitute a character and when the data begins and ends a synchronous zero data communication
like the new art is widely used for character oriented transmissions in the asynchronous method.
Each character such as ASCII characters is packed between start and stop it.
This is called framing their starts.
It is always one bit but it's stopped.
Bits can be one or two bits start but is always zero and the stop it is indicated by one for example
over here we send into ASCII character E which has the binary number 1 0 0 0 0 1 which we'll talk about
this other 0 later but there's a reason we have another 0 added here
as we can see the data is framed between the start speeds and to stop it stop it.
As we said are indicated by one and this starts it is always indicated by zero and a stop it can be
two in number by just by the Stop it is always one you can have one bit full stop or two bits full stop.
In this in this example we've got two bit four stop the rightmost bit or the LSP assent first the LSP
stands for the least significant bit in asynchronous serial communications peripheral chips can be programmed
for data that is 5 6 7 or 8 bits wide while in older systems ASCII characters where 7 bit the mode in
systems usually send non ASCII 8 bits data as well.
Now let's talk about parity in some systems in order to maintain data integrity that parity bits of
the character bytes is included in the data frame.
This means that for each character we have a single parity bit in addition to the start and stop bits.
The parity bits may be odd or even in the case of an order parity the number of data bits including
the parity bit has an odd number of ones.
Similarly in an even parity the total number of bits including the parity bits is even for example the
ASCII character a has the binary number 1 0 0 0 0 1 and with course serial included to the beginning
here of course you added here for even parity you R2 chips allow us programming of the parity bit for
odd even.
And in fact we can choose not to have parity at all.
When programming the chips and we shall see how to do this programmatically.
Now we look at data transfer the rate of data transfer in serial data communication is stated in BP
s or bits per second.
Another widely used terminology for BP s is the board rate.
However the both rate and BP s rates are not necessarily equal.
This is due to the fact that both rate is defined as the number of signal changes per second in modems.
It is possible for each signal to transfer multiple bits off of data but when we are talking about wired
connections like that you add that both rate and BP s are the same.
So this order is for this short.
Both of you on you art and the you art data transfer protocol.
If you have any questions just let me know.
I'll see you later.