what is RS232

[chagz]

Can anyone please tell me what the RS232 standard is. And, if possible, I would like to know any sites I could use to research on the topic

 

[ericgibbs]

Can anyone please tell me what the RS232 standard is. And, if possible, I would like to know any sites I could use to research on the topic

hi,
Look here: RS232 Communication – The Basics | eXtreme Electronics

 

[mneary]

See this thread.

 

[Syed Horr]

salaam

RS-232 stands for Recommend Standard number 232 and C is the latest revision of the standard. The serial ports on most computers use a subset of the RS-232C standard. The full RS-232C standard specifies a 25-pin "D" connector of which 22 pins are used. Most of these pins are not needed for normal PC communications, and indeed, most new PCs are equipped with male D type connectors having only 9 pins.

RS232 Communication – The Basics | eXtreme Electronics

https://www.electro-tech-online.com/custompdfs/2010/01/rs_232_serial_ports.pdf

What is RS-232?

 

[Sceadwian]

There is a bit of an issue with the term RS232. As Syed stated the current standard is RS232C requires +12 -12 volt line swings and won't register anything between +3 and -3 volts as a valid signal. The standard doesn't require all pins, it only requires a TX and RX line the rest are optional.

However almost no real world devices actually produce or require RS232C compliant signals. RS232 is more modernly used as a general term used when it's simple serial data, using a TX and RX line, often at simple 0 and 5 volt logic.

The bellow link may provide more information about how this type of serial communication typically works.
Serial port - Wikipedia, the free encyclopedia

The section about Data Parity and Stop bits explains the actual logic levels of a typical serial byte stream, the most common convention I've run across is 8N1 which is 1 start bit 8 data bits, no parity bit and 1 stop bit. The start bit is required. Some systems use more than 1 start bit or some kind of more complicated frame systems but generally at that point it's not considered RS232 anymore.

Typical RS232 logic is inverted meaning a low logic state is actually a high voltage state and a low voltage state is a high logic state.

 

[westom]

Can anyone please tell me what the RS232 standard is.

Many will not include this or know this. Teletypes once used 4-20mA current loops for communication to a modem. Bell System created an interface to connect modems (communication equipment) to terminals and computers (terminal equipment). The standard used voltage rather than current for data signaling. Was limited to (if I remember) less than 50 feet. And was only intended for modem connections. Handshaking signals also permitted modem and terminal equpment to know when a connection exists, data throttling, and even a ring indicator. Standard even made half duplex or full duplex communication possibe.

Most implementations of RS-232 were kludges. For example, DEC used a modified version, combined it with XON-XOFF to do data throttling, and connected to printers. From that kludge came a nine pin (kludge) version of the 25 pin RS-232.

An old joke: RS-232 is a "non-standard standard". And survived until a clearly superior standard -USB - from Intel and many friends finally replaced it.

 

[acc1444]

RS232 is a asynchronous serial communication protocol

 

[mneary]

RS232 is a asynchronous serial communication protocol

No, RS232 defines the physical layer: e.g. connectors, signal names, voltages, data rates, etc.

Protocol is not specified.