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RS 232 C & RS 449:

RS 232 C & RS 449 Samak Rizwan (01-133092-228) Fahad Tariq (01-133082-060) Data Communication

D-sub Connectors :

D-sub Connectors Family of plugs and sockets widely used in communications and computer devices. D-sub connectors, or DB connectors, are used to hook up computer and communications devices. D-sub connectors come with 9, 15, 25, 37 and 50 pins.

RS 232 :

RS 232 In telecommunications, RS-232 (Recommended Standard 232) is a standard for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Communication Equipment). It is commonly used in computer serial ports. In Electronics Industries Association (EIA )- 232 parlance, the device that connects to the interface is called a Data Communications Equipment (DCE) and the device to which it connects (e.g., the computer) is called a Data Terminal Equipment (DTE).

RS- 232 C:

RS- 232 C RS-232C is a long-established standard ("C" is the current version) that describes the physical interface and protocol for relatively low-speed serial data communication, between computers and related devices. It was defined by an industry trade group, the Electronic Industries Association (EIA), originally for teletypewriter devices. The C revision of the standard was issued in 1969 in part to accommodate the electrical characteristics of these devices. Almost all modems conform to the EIA-232 standard and most personal computers have an EIA-232 port for connecting a modem or other device. The EIA-232 standard supports two types of connectors : a 25-pin D-type connector (DB-25) a 9-pin D-type connector (DB-9).


Working RS-232C is the interface that the computer uses to talk to and exchange data with the modem and other serial devices. Somewhere in the PC, typically on a Universal Asynchronous Receiver/Transmitter (UART) chip on the motherboard, the data from the computer is transmitted to an internal or external modem (or other serial device) from its Data Terminal Equipment (DTE) interface. UART converts the data into parallel stream of bits. As the PC is a DTE agent, it also communicates with the modem or other serial device, which, in accordance with the RS-232C standard, has a complementary interface called the Data Communications Equipment (DCE) interface.

RS 449:

RS 449 The RS-449 specification, also known as EIA-449 or TIA-449, defines the functional and mechanical characteristics of the interface between data terminal equipment (DTE) and data communications equipment (DCE). The RS-449 interface is a further enhancement of RS-232 and RS-423. It is aimed at catering for very fast serial data communications at speeds up to 2 Mbps. For the RS-449 interface, ten additional circuits functions have been provided when compared to RS-232.


Working One of the ways in which the RS449 data communications standard is able to send at high speeds, without stray noise causing interference, is to use a differential form of signaling. Earlier data communications standards such as RS232, used signaling that was referenced to earth and while this was easier to implement and cheaper to cable, it introduced limitations into the system. RS449 is a high speed digital interface - unlike RS232 which uses signals with reference to ground, RS449 receivers look for the difference between two wires. By using “twisted wire pairs” for the data lines, any unwanted noise will be picked up by both wires together.

Slide 8:

This means that higher levels of noise can be tolerated without any degradation to the performance of the data communications system. The differential signals for RS-449 are labeled as either "A and B" or "+ and -” ; whereas wire A or + does not connect to B or -. Wire A always connects to A and B connects to B or + to + and - to -. If the wires are crossed, the data or clock in the interface, is inverted and it wouldn’t work any more.

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