Transmission Modes | Parallel and Serial

In this tutorial, we are going to see how communication between two machines can be done in different ways (Parallel and Serial). The transmission mode designates the number of elementary units of information (bits) that can be simultaneously transmitted by the communication channel. In fact, a processor (the computer in general) never treats only one bit at a time, it generally allows to treat several (most of the time 8, or one byte), this is the reason why the basic link on a computer is a parallel link.
 

 

Parallel Transmission:

A parallel connection is the simultaneous transmission of N bits. These bits are sent simultaneously on N different channels (a channel is for example a wire, a cable, or any other physical medium). The parallel link of computers generally requires 10 wires.
 

 
These channels can be :

• N physical lines: in which one physical line is used for each bit (this is why parallel cables are made up of several wires)
• a physical line divided into several sub-channels by dividing the bandwidth. Thus each bit is transmitted on a different frequency…

Since the wires are close to each other on a ribbon cable, there are disturbances (especially at high speed) that degrade the quality of the signal…
 

 

Serial Transmission:

In a serial link, data is sent bit by bit down the transmission path.
 

 
Since there are problems in parallel transmission, serial transmission is the most used. However, since only one wire carries the information, there is a problem of synchronization between the transmitter and the receiver, which means that the receiver cannot a priori distinguish the characters (or generally the sequences of bits) because the bits are sent successively. There are therefore two types of transmission that overcome this problem:

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