In my exploration of the world of technology, I’ve encountered many acronyms and technical jargon, and one term that has particularly caught my attention is the COM port.
If I’ve ever wondered what a COM port is and why it matters in my realm of computing, I’m in the right place.
In this article, I’ll dive deep into the history, functionality, and applications of COM ports, shedding light on their significance in my interconnected digital world.
Let’s start with our burning question: What Is A COM Port?
What Is A COM Port?
A COM port is my I/O interface, allowing me to connect a serial device to my computer. It is known as a serial port.
![What Is A COM Port?](https://www.motherboardfx.com/wp-content/uploads/2023/11/image-24.png)
While it’s true that most modern computers no longer come equipped with COM ports (I’ve noticed that almost all laptops with serial ports are no longer in use), I’ve encountered several instances where serial port devices are still in active use, relying on this interface.
I’ve encountered lab instruments, medical equipment, and point-of-sale systems that often utilize serial connections.
So, what exactly are COM ports? In my understanding, they serve as asynchronous interfaces that allow me to transmit one bit of data at a time when I connect them to a serial device.
The designation ‘COM’ originates from their role as communication ports on IBM-compatible computers.
In the context of traditional personal computers, I’ve noticed that I commonly used COM1 and COM2 to connect serial port devices like modems or mice.
- COM 1 works with a 9-pin D-shaped connector called the RS-232 interface.
- In contrast, COM 2 utilizes an old-fashioned DB25-pin connector, the RS-422 interface, which has become infrequently used over time.
They adhere to the MODBUS communication protocol. Typically, households do not utilize this interface; instead, the computer serial port (COM1) is employed for RS232 or 485 communications with the instrument to acquire data on the embedded industrial PC control.
Distinguishing itself from a parallel port, a serial port transmits its data and control information bit by bit. Despite a potentially slower speed, the transmission distance surpasses that of a parallel port.
Therefore, the serial port is the preferred choice for communication over an extended distance. Traditionally, there are two chassis, though newer models may feature only one. Laptops, likely, do not incorporate it.
Numerous industrial instruments incorporate it as a standard communication port. The instrument’s user manual typically outlines the communication’s content and format.
What Is A Serial Device?
Electronic devices, known as serial devices, are distinguished by how they transfer data. One bit of information is delivered and received at a time, making communication straightforward and dependable.
What Does A Computer’s Serial Port Mean?
![What Does A Computer's Serial Port Mean?](https://www.motherboardfx.com/wp-content/uploads/2023/12/image-1.png)
Many recently built desktop and laptop computers do not come with serial ports. The laptop may require a serial adapter. One or more USB interfaces are typically used in place of the RS232 serial ports that were once common.
This will not prohibit using a serial port device with a fresh PC. If your computer lacks an installed serial interface, you can use a USB-to-serial converter to add one or more COM ports.
There are numerous options, most simple and affordable to implement. On a Windows PC, the adapters are operated by installing a device driver.
The USB to RS232 converter can be used by the computer in place of a serial interface thanks to a program called a driver. A virtual COM port that functions exactly like a real port on a computer’s motherboard is created to do this.
What Is The Purpose Of Serial Ports?
USB connections have largely supplanted COM ports to transmit serial data faster. External serial devices are no longer necessary because internal modems are found in most PCs.
Similarly, data input via COM-connected mouse is becoming less common. Although not as common, null-modem cables can link two computers via serial interfaces.
There are still numerous specialised applications for serial ports. Monitoring devices and machinery for industrial automation applications are a couple of examples.
They use the RS232 interface, which is still supported by many contemporary computers’ hardware. We should expect the RS232 protocol to be around for a while because several affordable serial over Ethernet software and hardware solutions allow COM ports to be used on machines that do not have any.
Powering 15 metres of shielded cable is another benefit of having a COM port. The maximum length for a similar USB cable would be five metres.
1. Serial port types:
There are two common setups for serial ports. Typically, they are
- Male connectors with nine or twenty-five pins. 25 pin
- Female connections are used as parallel ports to attach a partner cable.
The standard convention for port naming on personal computers designates COM1 and COM2 for serial interfaces and LPT1 for parallel ports.
Every pin has a specific purpose, such as transmitting and receiving data or notifying a terminal-ready message. A serial port is any interface that complies with the RS232 protocol.
2. Serial port-using devices include:
Many manufacturers of devices use the RS232 protocol. Serial communication is a feature many devices have built-in, including barcode scanners, measurement equipment, industrial automation sensors, and GPS receivers.
3. UART:
Universal Asynchronous Receiver/Transmitter is referred to as UART. It is a piece of hardware that converts data between a computer’s parallel and serial ports. A byte of data is serially transmitted bit by bit via UART processing. The data is subsequently transformed back to a full byte at the other end of the link. When using this technology, data transmission via a parallel or serial connection is irrelevant.
What Is COM Header On Motherboard?
Communication ports have been around since 1969. It is a straightforward serial protocol developed with basic logic to fit the available technology at the time.
![What Is COM Header On Motherboard?](https://www.motherboardfx.com/wp-content/uploads/2023/12/image-2.png)
Your motherboard’s COM header can be represented by
- COM1
- COM2
- COM3
- COM4
Each with a different PIN and set of features. However, the main purpose of this header is to facilitate communication between a computer and other computers or an external device.
The COM header on a motherboard has two drawbacks:
- The protocol cannot identify a device and its capabilities
- It operates very slowly.
The USB protocol, which became widely used in the mid-1990s, is an advancement over this antiquated technology.
USB headers, common on contemporary boards, enable devices to recognise their class and function faster.
Because USB has become the de facto standard for peripheral connections, motherboards no longer need a COM port header. This helps explain why many PCs and laptops come with USB connections but no serial ports.
However, a COM header is still present on certain contemporary motherboards.
Wrapping Up:
In conclusion, COM ports may seem like a technical mystery, but they are the unsung heroes behind seamless device communication. From their humble beginnings to the latest advancements, these ports have stood the test of time, proving their relevance in the ever-evolving landscape of technology.
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FAQs:
Q1. What is the Purpose of the COM Port?
A COM port serves as a communication interface, utilizing a set of pins to facilitate data exchange between your computer and connected devices.
Q2. Can I Utilize My Ethernet Port as a COM Port?
A virtual serial port over Ethernet offers the complete functionality of a physical COM interface. It converts data bi-directionally, enabling network transmission, then reverts it to serial signals for interaction with devices and programs.
Q3. What are the Distinguishing USB and COM Ports?
The disparity between USB and COM ports lies in their complexity. USB surpasses RS-232, which solely delineates the physical (hardware) layer, by necessitating a comprehensive software protocol stack. It’s essential to note that “COM” is merely a device name prefix employed in Windows (and formerly in MS-DOS) for a serial (UART) port.
Q4. What is the maximum number of serial ports that can be concurrently shared over Ethernet?
With Serial over Ethernet software, you can share a serial port over a LAN or any other network, and the software supports simultaneous sharing of up to 500 ports.
Q5. Where is the COM port located on a PC?
To find your COM port number, follow these steps: Open Device Manager (Start → Control Panel → Hardware and Sound → Device Manager). In the Device Manager list, navigate to the ‘Ports’ category and locate the corresponding COM Port.”
References:
- https://forums.tomshardware.com/threads/what-is-a-com-port.395543/
- https://www.reddit.com/r/pcmasterrace/comments/iwmr59/what_does_com_mean_on_my_motherboard/
- https://superuser.com/questions/918882/what-are-com-ports-and-why-does-a-pc-need-them
- https://forums.tomshardware.com/threads/what-is-a-com-port.395543/