RS232 connectors – A Safe and Reliable Option for Your Network

An RS323 communication protocol is the oldest and most popular form of serial communication in applications like printers, computers, etc. Also, other communication forms may include an RS-485 interface and i2C. Choosing the best RS232 serial cable can be challenging for a few tech enthusiasts. But worry not because we've got you covered. Today's post discusses what a regular RS232 contains in its datasheet, like the pinout and applications of the RS232 connector.  

What are rs 232 Connectors?

RS232 connector, or a D-type connector, is a serial interface port that permits an exchange of data between devices.

Its design allows data exchange between Data Communication Equipment (DCE)/MODEM and Data Terminal Equipment (DTE)/ PC. Again, it solves the challenge of parallel communication. 

RS232 devices often use serial communication data with a bit-by-bit exchange of data. Moreover, it's a nine-pin connector piece.  

RS232 Connector Types

25-Pin Type D Subminiature (DB25)

The original RS232 standard introduced in 1960 specified this 25-pin D-subminiature connector to connect DTE and DCE devices.

This standard divided the pins into control, transmission, and ground pins to handle the connection and data transfer between the devices.

An RS232 DB25 connector

9-Pin DE-9 (DB9)

The 25-pin D-sub connector had 20 control pins, which proved more than enough because most serial devices did not use them.

So naturally, this tinier connector emerged to connect devices like joysticks, keyboards, and mice to computers.

DB9 male and female connectors (note the nine pins and ports)

DE-9 connectors were also typical in IBM-compatible computers for digital RGBI video-display outputs.

DE-15 Connector (DB15)

DE-15 connectors replaced DE-9 for analog video (VGA, SVGA, and XGA) transmission to monitors and projectors. The connector also provided a serial link for game controllers like joysticks.

DB15 connectors for a VGA cable

Although it has more pins than the DE-9 connector, the DE-15 plug has the same D-shell size.

Rs 232 Pin Configuration

A DB9/RS232 connector pinout comprises nine pin connections arranged in its port. Initially, it was a 25-pin port terminal, but you can now find a 9-pin terminal. 

Furthermore, DTE and DCE RS232 ports have similarities because their data flow direction differs. 

The nine pins are in three different categories.  

Category 1: Data pins 

The first category is data pins that conduct data flow and include;

Pin2/ RDX/ Receiver pin – Receives data or the actual signal.

Pin3/ TXD – It transmits data.  

Category 2: Control pins 

The second group avoids data loss and establishes an interface and consists of; 

Pin1/ CD (Carrier Detect) – The MODEM cables set the CD pin to receive an answer transmitted by remote MODEM.

Pin4/ DTR (Data Terminal Ready) – The second pin receives instruction from the PC to prepare the MODEM to connect with a telephone circuit.

Pin6/ DSR (Data Set Ready) – The MODEM often instructs the DSR to inform the PC of its readiness to receive and send data.

Pin7/RTS (Request to Send) – It receives instructions from the PC to notify the MODEM to send data.

Pin8/ CTS (Clear to Send) – MODEM sets the CTS; it becomes ready to receive data/answer signals through the PC.

Pin9/ RI – Lastly, pin9 gets directions from the MODEM cables to inform the PC of a ringing condition. 

Category three: Reference pin

A reference pin solely includes the GND/ ground pin, a reference point for all pin voltage signals.  

Rs 232 Connectors Features and Specifications

RS 232 connectors have several specifications and features, as discussed below.

• First, you can establish a 2-pin simplex RS232 interface if needed.
• Then, you can establish the interface to about 50ft distance.
• RS232 connectors use asynchronous communication. Therefore, they don't share clocks between a MODEM and a PC.
• In addition, the wide voltage range of the logic is convenient for users. For instance, logic 0 on the pin has a voltage range from +3V to +15V. Whereas logic 1 ranges from -15V to -3V.
• You can also use RS232 to achieve a maximum data transfer speed of 19 kilobits per second (Kbps).
• Slew rate – A slew rate is a rate of change in signal levels. An RS232 serial connection has a slew rate reaching 30V/microsecond and 20kbps maximum bitrate.
• Moreover, the RS232 pins can generate a maximum current of 500mA.
• Additionally, the full-duplex interface or an RS232 is efficient.
• Lastly, you can install an MAX232 IC easily to establish the RS2232 interface having microcontrollers.

How to use the RS 232 Connector?

Under any circumstances, we can't directly connect an RS232 connector to a controller. Instead, we use a MAX232 IC.

Circuit diagram with a microcontroller, MAX232, and RS232 serial port  

Let's take a look at the circuit diagram above as an example.

We use an MAX232 converter chip to connect the controller to the female RS232. The communication voltage can range from -15V to +15V or from -1 volt to +12 volt.

The IC converts high-voltage RS232 signals to TTL and vice versa. Since the varying voltage level doesn't suit sensitive electronics, the MAX232 chip becomes a mediator. So, without it, you can cause permanent damage to one of your devices.

• Applications
• Modem connections,

(RS232 cable connecting to a modem)

• Motor control units,
• Memory devices,
• Telephone lines,
• Automatic control systems,
• Battery management system,
• Stenography or stenotype machines,
• Transfer of serial data,
• Servers,
• Personal computers, and
• Printers where you use one handshaking line and data lines.

(printer and scanner)

Are there any Disadvantages to the RS 232 Connector?

The short answer is yes. You will find some factors not favoring your application for an RS232 connector. They include:

• First and foremost, it lacks a Vcc, a pin required to power devices.
• Additionally, unlike a 12C, you can only connect a single device to an RS 232 connector.
• Moreover, its maximum distance of 50ft and a maximum speed of 19 Kbps disfavors several applications.
• It also has many communication pins. And more hooks equal more noise levels.
• Switching between +15V and -15V voltages is hard at higher speeds despite having a wide voltage range.
• Finally, it requires hardware to convert its high-voltage logic to comply with TTL. (TTL/LAN converters involve processor units and controllers).

RS232 vs. RS422 vs. RS485: What Is the Difference?

RS232 vs. RS422

The Electronics Industries Alliance (EIA) introduced the RS422 standard in 1975 to replace RS232-C, the fourth version of RS232.

This new standard was more efficient because it used lower voltages (-6V to +6V vs. -15V to +15V) and differential signaling to handle faster signal transmission.

Also, it could transmit signals across longer cable lengths with minimal EMI or RF noise interference.

Although the standard specified the DB-25 connector, manufacturers could customize the interface because RS422 focussed on the electrical characteristics of the signal transmission.

The DE-9 connector (industry standard for RS422 connectors)

Companies like Apple initially used a 9-pin D connector to connect Mac computers to AppleTalk networks and peripheral devices. But later versions had an 8-pin mini-DIN plug.

What About RS485?

RS485 is a newer standard than the other two because the TIA and EIA published it in 1983.

Unlike the other two, this standard defines the electrical characteristics of receivers and drivers in serial communication.

RS485 balances electrical signaling and supports multipoint systems, allowing multiple drivers and transmitters to communicate on the network.

A 9-pin connector for data transmission using the RS485 standard using the RS232 protocol

Unlike RS422, RS485 supports a true multipoint network because it allows a maximum of 32 drivers and 32 receivers. RS422 can only handle one driver and ten receivers max.

This communication occurs in half-duplex mode across a twisted-pair cabling network.

But you can make it full-duplex using two twisted pairs (four wires) across the network.

Here’s a summarized comparison of the three standards.

RS232 FAQs

How to Connect RS232 to a USB port?

You’ll need a USB to RS232 converter to handle this connection. The converter connects to your computer via the USB plug, while the other end (RS232) hooks up to the RS232 device via a multi-pin serial port.

A 9-pin RS232 connector to USB port converter

What Type of Cable is Used for RS232?

Straight-through or crossover cables (null-modem), with the most common type being straight-through. This cable connects Data Terminal Equipment (DTE), such as a computer, to Data Circuit Terminating Equipment (DCE), such as a modem.

Crossover or null-modem cables connect two like devices, such as two DCE or DTE devices.

What is the Difference between RS232 and RS232C?

The 1960 RS232 connector standard is the original Recommended Standard (RS) and has undergone several revisions.

Each revision gets a letter suffix, meaning RS232-C is the fourth version.

This interface can link unlike (DTE to DCE) or like devices (DTE-DTE or DCE-DCE) using straight-through or crossover cables.

Conclusion

RS232 connectors operate in several applications. For example, their connection plays a role in personal computers' uninterruptible power supplies and data storage. You can also find them in modems, which are peripheral devices. 

Do you have any questions or need clarification? Contact us, and we'll get back to you soon.