Introduction
Hello, my name is Gu. It is spring according to the calendar, but I am still shivering in the cold.
This time, I would like to talk about serial communication using UART.
What is UART ( U niversal A synchronous R eceiver T ransmitter ）?
A communication circuit that converts serial signals to parallel signals and vice versa.
Here is a word I don't understand.
What exactly are "serial signals" and "parallel signals"?
They are signals (data) exchanged in serial or parallel communication.
Since it is not clear what serial communication and parallel communication are, we will explain the difference between serial and parallel communication below.
About Serial and Parallel Communications
Serial (continuous) communication is...
Serial communication is a communication method in which characters are carried in a vertical line in sequence.
To be precise, one bit of data is sent per clock cycle.
(Note: One square in the above figure is considered to be one bit.
On the other hand, parallel (simultaneous) communication is...
This is a communication method in which characters are sent in a horizontal line all at once.
To be precise, the number of bits sent in one clock is two or more (e.g., 8 bits).
(The number of bits that can be sent and received in one clock cycle depends on the environment.)
(Note: A square in the above figure is considered to be one bit.
Looking at it this way, does it not seem more convenient to carry (send/receive) a lot of characters at once with parallel communication than with serial communication?
However! In fact, serial communication is more mainstream than parallel communication!
Why is that?
The key to solving this mystery lies in "faster communication speed”.
Why serial communication is the mainstream
Consider parallel communication.
When receiving 8-bit data, all bits of data would normally be received in the same order as shown in the figure above.
However, what would happen if the wiring were as shown in the figure below?
The length of the wiring will change due to the bending of the wiring.
This difference in wiring length causes a subtle change in the data arrival time,
As shown below, all bits are not received at the same timing.
(Note: One square in the above figure is considered to be one bit.
If the communication speed is slow (i.e., the interval between clocks is wide),
there is no problem because all data is received between the first and second clock cycles.
However, as the communication speed increases (i.e., the interval between clocks becomes narrower),
it becomes impossible to send all the data in a single clock cycle.
With serial communication, no matter how fast the communication speed, data is received one bit at a time in sequence, so there is no problem as with parallel communication!
For this reason, serial communication has become more major than parallel communication in these days of faster communication speeds.
Conclusion
The difference between serial and parallel communication is the size (number of bits) of data that can be sent and received in one clock cycle. Serial communication is becoming the mainstream due to faster communication speeds.
Gu's tweet
I'm surprised that the way the wiring is bent affects the data transfer speed.
Appendix
There is a device called "equal-length wiring" as a way to equalize the data transfer rate when doing parallel communication.
This is called "equal-length wiring".
By equalizing the length of the wires, all data is sent and received at the same time.
Unexpectedly familiar serial communication
A typical UART is National Semiconductor's 16550A.
RS232C and other serial communication standards are also available.
I am sure you have all seen them at least once!
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