RS232 and DB9 are two interconnected terms for serial communication, specifically for computers, printers, and modems. RS232 and DB9 are data connectors with different features and uses. In this post, we will cover details for RS-232 and DB9 to help you understand their differences. Let’s get started with RS232 vs. DB9.
What is the RS232 protocol?
- RS in RS232 stands for recommended standard and defines serial communication using DTE and DCE signals. DTE is data terminal equipment, and DCE is data communication equipment.
- The DTE devices are a computer, and the DCE is a modem. It is defined as the interface between DTE and DCE is made with the use of serial binary data exchange.
- DTE transmits data in series form to other instruments, DCE. DTE transmits binary data 11011101 to DCE, and then DCE transmits binary data 11010101 for the DTE device.
- RS232 defines common voltage levels, operation modes, and bits transmitted from DTE to DCE. This standard is used for the transmission of data exchange through a telephone line.
Working of RS-232
- The RS232 working is defined through the protocol format. RS-232 is a point-to-point asynchronous communication protocol and transmits data in one direction.
- It does not need any clock for synchronization of the transmitter and receiver. The data format is a processed start bit that has 7-bit binary data, a parity bit, and a stop bit that are transmitted in sequence.
- Transmission started with transmitting the start bit 0. That succeeded with 7-bit ASCII data.
- The parity bit is applied to the data for the receiving process. The data transmitted from the transmitter is matched to the receiver.
- Transmission is stopped through the use of a stop bit and denoted with the binary number 1.
- 1 or 2 stop bits transmitted.
- In the diagram below, the ASCII character A is sent using a serial binary stream of 1s and 0s, and the data is sent with some delay in each bit.
- That delay is inactive time, and RS232 line is negative logic state or (-12V).
What is a DB9 Connector?
- The DB9 is a commonly used type of connector, which is a D-Sub type of connector.
- DB9 is a small-sized design of D-subminiature connectors and comes with 9 pins as a male connector and 9 pins for a female connector.
Uses of DB9 Connectors
- DB-9 connectors are commonly used for personal computers and servers. These modules are made to operate with the EIA 232 serial interface standard, which defines the operation of all 9 pins as standard, so different manufacturers can make their devices according to them.
- DB9 connectors are used for serial peripheral devices such as mice, joysticks, and keyboards. They are also used for DB9 cable assembly data connections.
- Now in different applications, DB9 is replaced with different interfaces like USB, PS/2, Firewire, etc.
RS232 3D Model
DB9 3D Model
RS232 VS DB9: Differences
RS232
RS232 Features
- The main features are molded hoods and come with thumbscrews for making strong connections.
- It has straight-through wiring that is configured with 9 pins of RS232.
RS232 Advantages
- RS-232 interfaces are commonly used for connection with different legacy devices. It is mainly used for point-to-point connections for DTE and Communication Equipment (DCE) devices.
- It is also used for making long-term communication, about 50 feet for low baud rates and supported error correction features.
- It also has noise immunity and uses ± 12 volts or higher for binary logic 0 and logic 1.
- It is a low-cost interfacing option.
Disadvantage of RS-232
- RS232 is used for system-to-system communication but is not used for chip-to-chip or chip-to-sensor device protocols.
- It is compatible with low-speed for longer-distance applications, high-speed such as 115200 baud, and also used for short distances.
- RS232 unbalanced transmission.
DB9 Features
- DB9 provides 9-pin serial connections for data line surge suppression of data terminal, data communications equipment, personal computers, modems, etc.
- It has reversible features for use with male or female captive DB9 ports.
- It has protection for all 9 data lines with D shell chassis.
DB9 Advantages
- DB9 connectors come with many features; they can be customized with 9 pins for carrying serial data.
- The speed of this connector is lower than other modules such as USB, and it also has longer-length cables.
- The USB comes with a 5-meter length feature; RS-232 is used for serial data, which does not have a certain defined length value.
- For older devices that have DB9 connectors, there are many options.
- Converters of other standards, such as USB and Ethernet, also help to use devices on computers.
DB9 Disadvantages
- They are a larger size connector that is not easy to connect and disconnect in all applications.
- Their pins are open and exposed so they can be damaged. We can connect the connector without the use of screw hardware, but pins can hold in the connected devices. If we use the thumbscrew, it will take a longer time for connection and disconnection.
- Serial communication is slow and an older technique for data communication. For longer-length cables, speed is slow. That affects communication and causes PC software to freeze. So DB9 cables are not preferred over others due to this issue.
DB9 Limitations
Limited Pin Count:
- 9 pins for the DB connector restrict signals transmitted at the same time as connectors that have many pins. The larger pin connections are limitations for these applications since DB9 does not fulfill their demands.
Signal Quality:
- Noisy conditions can affect the quality of the signal transmitted through DB9 connectors since they are susceptible to electromagnetic interference (EMI).
- If the DB connector is not grounded accurately, signals are distorted due to communication errors.
Legacy Compatibility:
- Ethernet and USBs are used as replacements for different applications than the DB9 connector. So it is a legacy interfacing module. So new devices that do not have DB9 ports are not connected with a DB9 connector.
Limited Data Transfer Rate:
- High-speed data transfer devices do not use DB9 connectors since they do not support these features.
Rs232 Limitations
Data Transfer Rate:
- As compared to modern communication protocols, data transfer rates is low for RS232 communication system. The devices that were used for high-speed data transmission did not use RS-232 since it has high data interfaces at a range of some megabits per second.
Number of Connections:
- The RS-232 network handles limited devices according to its point-to-point communications. There is a need to increase the number of connections with the use of serial multiplexers or converters
Attenuation
- It also has noise and attenuation issues since for longer distance transmission, then the signal of RS232 is affected. For longer distance transmission, the signal is not properly transmitted if the modules are not handling the signal and face attenuation and noise issues that affect the signal quality.
Complex Wiring
- For signal transmission and receiving, it needed multiple wires. So complex wiring process causes high installation and maintenance charges.
FAQs
Is DB9 like RS-232?
- RS232 is a serial interface, while DB9 has 9 pins. The RS232 connector is used with applications of these connectors.
What computer cable has 9 pins?
- DB9 comes with 9 pins.
What is the difference between DB9 and DB25?
- DB9 is a 9-pin connector, and DB25 has 25 pins. It is used for peripheral devices like serial printers, game controllers, and modems.
What is an RS-232 cable?
- RS232 is a standard protocol used for performing serial communication and is also used for the connection of computers and peripheral devices that helps for serial data exchange. These connectors are also called DB9 connectors as serial ports and come with two types: male connectors (DTE) and female connectors (DCE).
How do I connect DB9 with my laptop?
- Connect the serial DB9 end of the console cable in the serial DB9 port on the laptop. If the laptop does not have a serial DB9 port, connect the serial DB9 end of the console cable to the serial DB9 end of the USB with the serial DB8 adapter and then connect the USB port of the laptop.
How Does RS232 Work?
- The RS232 communication protocol is working based on computer serial communication. It is part of the required point-to-point asynchronous communication.
What are the disadvantages of RS-232?
- The RS232 comes with low data communication speed, negative and positive signal voltage affecting power supply design, and limitations for single master and slave. It causes noise due to unbalanced transmission.
Read also
