Serial communication can be defined as the method of sending one bit of data at one point of time in succession through a bus.
This is directly opposite to the function of parallel communication, where several bits are sent together on a bus consisting of many wired lanes in parallel.
As the cost of establishing a parallel communication is very high and moreover its configuration is lengthy and complex, the Serial communication is preferred for all major communication/computer networks. At small distances, serial buses are becoming more common and popular because the disadvantages of parallel buses prevails their advantage of simplicity. Improved technology to ensure the integrity of signal and increased transmission and receiving speed of data per channel has made the serial ports a close competitor to parallel ports.
The cost of integrated circuits are a lot because of the large number of pins. It is therefore, many integrated circuits utilize the serial buses when the importance of speed does not exist. Examples of these low cost serial buses are SPI, I²C, and 1-Wire.
Comparison with Parallel ports/buses
If you are thinking that the serial ports/buses are slower than parallel ports/buses as the transmission of data is only a bit per unit of time, then you are wrong. You will be surprised to know that the serial ports/buses may be clocked considerably at quicker rate than the parallel ports/buses than parallel links and can accomplish a higher speed of data flow. The factors which makes the serial ports/buses better than the parallel ports/buses are :
- In case of unclocked and asynchronous type serial ports/buses, the problem of clock skew between the lanes/channels does not exist.
- The serial communication configuration requires less space because the requirement of cable is less in serial connection. The availability of this additional space gives good isolation of the data lanes from the neighboring communication components.
- There is a minimal presence of conductors in the nearby space. It is therefore, the chances of crosstalk are rare.
- The cost of serial link is less in comparison to parallel links.
Few examples of systems consisting serial communication are :
- Morse code telegraphy
- RS-232,RS 422, RS-423 and RS-485
- Universal Serial Bus
- Serial Attached SCSI
- Serial ATA
- PCI Express
And many more….