what is RS 232 protocol?

Question

how I can interface serially throgh computer.

Answer 1

It is a "Standard" used for communication for the "DB-9" (9 Pin connector not 25 pin) RS-232 connectors on your computer. The "RS-232 connector is "Series" connected and can only transmit information using 2 lines TD and RD (along with a few "Control" lines to keep things in order)

The amount of information that can be transmitted using this method is restricted. So it is usually used for your printer or other devices where high speed data transfer is not an issue.

This is in stark contrast to "Parallel" ports that can transmit at high bit rates.

Answer 2

RS232 is a protocol for communications between pieces of computer equipment.

The hardware form consists of between 3 and 9 wires.

In it's simplest form, it involves 3 wires - Transmit, Recieve, and Ground (or common). As it was originally developed for modems, there are additional signals used by some systems such as "clear to send," "ready to send," and "data set ready."

Data is transmitted between the two devices by means of electrical pulses. A 0 is represented by no voltage, and a 1 is respresented by +5 volts. How long the signals last is determined by BAUD rate. The higher the baud rate, the faster the electrical pulses that create the signal.

Data transfer is usually accomplished in bytes, which are packetized based on "start bits," "data", "parity," and "stop bits."

8N1 is the abbreviation for 8 data bits, no parity, and 1 stop bit.

To send the number 1 over an 8N1 scheme, the pulses would look like this:

1 start bit = +5v
0 high data bit
0
0
0
0
0
0
1 low data bit
0 no parity, so it's always zero
1 stop bit.

How long the pulses last depends on BAUD rate, as mentioned earlier. At 100 BAUD, you transmit 100 bytes per second (which is not exactly 100 bits, as each byte takes 11 bits to transmit).

Since RS232 is mainly a hardware standard, generally there is a "Transport Protocol" which is overlayed on top of it to actually define what a data packet means.

Some typical transport protocols are X-Modem, Y-Modem, K-Modem.

Hope this gets you started. You really have to know what protocol the device you want to talk to speaks in order for RS232 to be useful.

Answer 3

In telecommunications, RS-232 is a standard for serial binary data interconnection between a DTE (Data terminal equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports. A similar ITU-T standard is V.24. RS is an abbreviation for Recommended Standard.

DTE is an abbreviation for Data Terminal Equipment, and refers to an end instrument that converts user information into signals for transmission, or reconverts the received signals into user information. A DTE device communicates with the Data Circuit-terminating Equipment (DCE). The DTE/DCE classification was introduced by IBM company.

A DTE is the functional unit of a data station that serves as a data source or a data sink and provides for the data communication control function to be performed in accordance with link protocol.

The data terminal equipment (DTE) may be a single piece of equipment or an interconnected subsystem of multiple pieces of equipment that perform all the required functions necessary to permit users to communicate. A user interacts with the DTE (e.g. through a Human-Machine Interface), or the DTE may be the user.

Usually, the DTE device is the terminal (or a computer emulating a terminal), and the DCE is a modem.

DTE is usually a male connector and DCE is a female connector.

A general rule is that DCE devices provide the clock (internal clocking) and that the DTE device synchronizes on the provided clock (external clocking). D-sub connectors follow another rule for pin assingnment. DTE devices usually transmit on pin connector number 2 and receive on pin connector number 3. DCE devices are just the opposite: pin connector number 2 is receiving and pin connector number 3 is transmitting the signals.

examples of Data Terminal Equipment:
http://www.nextag.com/data-terminal-equipment/search-html?nxtg=58100a1c0508-304CF1324D7A6E9A

Answer 4

A useful tool that most of the protocol analyzers were designed for, it will log all the communications between 2 devices, which allows programmers to understand / be familiar with or troubleshoot the protocol used between the devices, many of our customers use this feature for "reverse-engineering" as some software or firmware does not come with protocol manual.

The software comes with the features of viewing received data in different formats, namely Hexadecimal, Decimal, Octal, Binary and AscII codes. All data captured in monitoring mode are time-stamped

GO 2 THIS PAGE http://www.232analyzer.com/232/APP.HTM

Answer 5

It is a hardware standard, used for connecting to older modems via a 25-pin connector. The essential elements are that signals go one way on pin 2, the other way on pin 3, and the common return is pin 7. Other pins are used for each device to tell the one on the other end that it is ready to do busiiness. It is basically obsolete, being replaced by USB.

Answer 6

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