Serial communication is the process of sending and receiving data via communication channel bit by bit sequentially, one bit at a time.
Serial communication is used for all long-haul communication and most computer networks, where the cost of cable and synchronization difficulties make parallel communication impractical.
Main advantages of serial communications:
- fewer interconnecting cables (e.g. wires/fibers) and hence occupies less space. The extra space allows for better isolation of the channel from its surroundings;
- less crosstalk, because there are fewer conductors in proximity.
Data sent serially this way. When 8-bit data set D0..D7 is transferred into the output buffer to be transmitted, usually it is still in parallel form. This output buffer converts this data into Serial data (PISO) (Parallel In Serial Out), MSB (Most Significant Bit) first or LSB (Least Significant Bit) first as according to the protocol. And than data is transmitted in Serial mode via communication channel (cable, radio etc.). When this data is received by recipient in its receiver buffer, the receiver buffer converts it back into parallel data (SIPO) (Serial In Parallel Out) for further processing:
Generally, all serial protocols can be divided into two groups: synchronous and asynchronous.
A synchronous serial communication is always coupled with a CLOCK signal, so that all devices on the serial bus share a common clock. This particular configuration allows a simpler and often faster data transfer, but also requires an additional channel to communicate. I²C and SPI are two synchronous serial communication protocols.
An asynchronous serial communication, on the other hand, does not use an external CLOCK signal and therefore requires less I/O channels for communication. At the expense of this, a reliable system for transmitting and receiving data must be implemented. The most common serial protocols are Bluetooth, Xbee, GPS module.
More information:
https://en.wikipedia.org/wiki/Serial_communication
Asynchronous serial communication
Universal asynchronous receiver-transmitter
Synchronous serial communication
Universal synchronous and asynchronous receiver-transmitter
