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Is HDMI Serial Or Parallel?

Is HDMI Serial Or Parallel?

High-Definition Multimedia Interface (HDMI) technology is a marvel and a revolutionary innovation in data transmission technology. The cable connection transmits uncompressed video and compressed/uncompressed audio between sender and receiver devices. 

Today, we look at how the technology works with keen detailed interest on whether the communication type is a serial or a parallel. Keep reading for comprehensive answers to all your HDMI-related questions.

So, is HDMI a Parallel or a Serial?

The simple direct answer is HDMI runs a parallel connection. The reasoning is concerning how it transmits data between devices.

A parallel connection sends data in multiple bits over multiple channels simultaneously. The working principle of a parallel connection allows it to transmit data faster and efficiently.

How Does HDMI Work?

a black HDMI cable


The HDMI technology works to maintain audio and video quality coming from the sender, for example, an HD-DVD player. Quality maintenance is possible because of the integrated Transmission Minimized Differential Signaling (TMDS) feature. 

TMDS encodes data transmissions over serial connections to prevent electromagnetic interference within the cable. The information transmission includes time information used to recover any lost data. A process called clock recovery.

Since HDMI cables consist of a twisted cable pair, they work together by one carrying the actual signal information. The other cable transmits a reverse version of the data so that HDMI technology can measure it against the original copy.

That is how it compensates for any lost information while transmitting.

HDMI has a High Bandwidth Digital Content Protection (HDCP) system for security. 

The system works by inspecting the encrypted source information to ensure it matches the decryption key in the recipient device. The procedure of encryption and decryption is also known as a handshake.

If an interception attempt or a change of encryption information, the sender device kills the communication process. 

Sometimes the feature malfunctions and stops legitimate transmissions, and you can solve it by rebooting your device.

What are Serial and Parallel?

In the tech world, specifically in data transmission, serial and parallel refer to how information goes from one digital device to another. Information can be sent from the host in bits either over a single channel or multiple channels.

1. Serial transmission

a VGA cable connect to laptop

A serial transmission involves sending data sequentially over the same channel a bit at a time. 

The data bits assemble as a unit before transmission in bit-by-bit form from the sender. The recipient must have received the initial data bit at the destination to receive the next bit.

The receiving device then dismantles the data upon receiving all the bit information.

A serial transmission transfers data at a slower rate than a parallel connection. Serial transmissions are generally helpful for long-distance data transfers.

Serial transmission has two varieties. They are;

Synchronous serial transmission

In this communication format, the transfer happens constantly and continuously under the dictation of a master clock signal. It sends data bits along the communication channel each time there is a clock pulse. 

Therefore, data transmission accuracy is highly dependent on the timing of both devices being in sync. As a result, there are fewer timing mistakes and faster data transfer. 

Asynchronous serial transmission

Here data bit transfer happens without the help of a clock signal. Instead, each device has a clock that works independently.

To synchronize transmission, the sender uses start and stop bits. Upon receiving the data, the recipient removes the start and stop bits. 

To transmit, the sender converts information into a parallel that the recipient will change back to a series upon reception.

2. Parallel transmission

connect HDMI cable to HDMI port on TV

Unlike a serial transmission, a parallel transmission uses multiple channels simultaneously. The message uses various channels that are within a cable. Therefore, a parallel communication cable is a single cable that contains multiple wires within.

The multiple channels give it an advantage over serial communication since a parallel can transmit more data bits faster.

A parallel transmission does not need to convert information to a series and then back to a parallel for data transmission to work.

However, the need for multiple channels increases the production cost of a parallel communication channel.

3. What are serial and parallel ports?

Generally, ports refer to the start and endpoints for communication connections. They are physical parts that allow you to connect devices to other peripheral devices either as an input or output.

USB ports are slowly replacing both the serial and parallel ports as the USB technology is much faster.

Serial port

Simply put, a serial port is a socket that allows you to connect a serial interface for data transmission. A serial port transmits a byte of data after breaking it into bit form and transferring it bit by bit.

Serial ports are also known as communication (COM) ports. They can comprise 9 or 25 pins that give them their multi-directional quality.

a serial port

A serial port is a male port because it acts as a plug and has a pin as a center conductor.

Parallel port

On the other hand, parallel ports are sockets for parallel interfaces in data transmission. The name comes from their multichannel way of transmitting data.

They are female since they have a center conductor with a hole for the male connector’s pin.

Parallel ports have 25 pins, and primarily, you can find them on printers, external hard drives, and scanners.

a parellel port on printer

Since technology is ever-evolving to provide faster, more straightforward solutions, there has been advancement in communication channels to patch the shortcomings of the older ones.

They include the ethernet and the USB. We will now look at them and see whether they also employ serial and parallel technologies.

Universal Serial Bus (USB)

The purpose of the USB invention was to make a more user-friendly connection type compared to the traditional varieties that existed. Modern devices come with a USB port for connecting peripherals like a mouse, keyboard, and even USB drives.

a white USB cable connecting USB port on laptop

USB got rid of the need for a particular port type for a specific kind of connection. The name ‘universal’ shows that you can use the port with various devices.

Among the many advantages, USB can support various forms of data hence its high utility.

It works by detecting when you insert a peripheral device and determining the type so that the system can allocate appropriate drivers.

It also has hot-swapping capabilities, which refer to the ability to insert and remove a USB device without rebooting your device.

The data transmission is in packets consisting of 1000 to 1500 bytes.

Within the data transfer is information on the destination, origin, length and any error within the data.

USB has a variety of versions, with each version being an advancement of the previous. They are USB 1.0, 1.1, 2.0, 3.0, 3.1 and 3.2. 

various versions of USB

A USB cable has wires within it with specific functions. Two are for power transfer and the rest transfer data.

Now that we know how the USB works, it is still unclear whether it is a parallel or series. The paragraph below takes care of that question.

Is USB Parallel or Serial?

USB is a serial connection. The ‘S’ in the name is one of the giveaways. The host device serializes the information where it has to handle parallel communication. 

Then communication occurs, and the recipient device turns the data back to parallel.

The functioning of different wires within a USB cable also reveals it is a serial connection. They are color-coded to match their role.

  • The red wire, or sometimes orange, transmits 5 volts of DC power. 
  • The black one is the ground wire.
  • The white wire transfers data as positive.
  • The green, sometimes blue one transfers data as a negative.

A keen look at the USB components reveals that they serve similar functions to those in a serial connection.


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However, advancements in USB technology allow it to send information between devices simultaneously. Thus, having parallel characteristics.

Alternatively, an ethernet connection can also establish communication between devices. The million-dollar question is ;

Is Ethernet Communication Serial or Parallel?

cables connection on a router

To classify an ethernet connection as a serial or parallel would be an injustice. The reason is that an ethernet connection has both serial and parallel properties.

For instance, a router can have multiple outgoing connections, thus presenting parallel properties. It can also show serial properties since data transfer happens via a pair of wires.

Also, note that serial communication cannot sustain the same amount of data an ethernet communication transmits.

Later versions of ethernet can also transmit data between devices simultaneously.

Final thoughts

To conclude, we have seen the advantages and disadvantages of communication types. We can now compare and contrast their features by chronologically looking at how they emerged and evolved to fit the current world’s standards.

Hopefully, you have all your answers about serial and parallel communications and understand how they work.

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