Sliding over ๐‘๐’-๐Ÿ๐Ÿ‘๐Ÿ



It is used for the Serial interface. Other devices can be controlled through the terminal for text interface through RS 232.

It was introduced in 1960 and since its introduction, it was known as ๐‘๐’-๐Ÿ๐Ÿ‘๐Ÿ but it is now officially called ๐“๐ˆ๐€-๐Ÿ๐Ÿ‘๐Ÿ.

The TIA-232 describes mostly the ๐Ÿ๐Ÿ“-๐ฉ๐ข๐งย  connector, the ๐Ÿ—-๐ฉ๐ข๐ง connector description is also available. The 25-pin connector was not of much use, so the manufacturers started to use the 9-pin connection.

The original standard i.e the 25 pin connection has a secondary tx/rx. Itโ€™s 2 interfaces in 1.

Although the RS232 ย ย ๐๐จ๐ž๐ฌ ๐ง๐จ๐ญ ๐ฎ๐ฌ๐ž ๐ญ๐ก๐ž ๐œ๐ฅ๐จ๐œ๐ค ๐ฌ๐ข๐ ๐ง๐š๐ฅ, the original 25 pin interface uses some clock signals such as
ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย – Transmit clock from DCE
ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย – Receive clock
ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย – Transmit clock from DTE

๐“๐ก๐ž ๐Ÿ—-๐ฉ๐ข๐ง ๐œ๐จ๐ง๐ง๐ž๐œ๐ญ๐จ๐ซ ๐ฐ๐š๐ฌ ๐ฌ๐ญ๐š๐ง๐๐š๐ซ๐๐ข๐ณ๐ž๐ ๐š๐ฌ ๐„๐ˆ๐€/๐“๐ˆ๐€-๐Ÿ“๐Ÿ•๐Ÿ’

โ€œRS-232 is an interface between Data Terminal Equipment and Data Circuit Terminating Equipment Employing Serial Binary Data interchange.โ€



The RS 232 uses 2 conditions, the ๐’๐ฉ๐š๐œ๐ข๐ง๐  ๐‚๐จ๐ง๐๐ข๐ญ๐ข๐จ๐ง and the ๐Œ๐š๐ซ๐ค๐ข๐ง๐  ๐‚๐จ๐ง๐๐ข๐ญ๐ข๐จ๐ง.

This terminology comes from the era of telegraphs/paper tapes where the marking condition means the mark/hole on the paper and the spacing condition means an empty region on the paper.

A simple working example would be:

When a key is pressed and if you capture a single shot signal on the oscilloscope, a signal will be generated spanning from -๐Ÿ”๐• ๐ญ๐จ >+๐Ÿ‘๐•.

ย ย ย ย ย ย ย ย ย ย ย ย ย ย For the interchange of signals, it is said to be in marking condition when the signal is greater than -3 Volts w.r.t to Signal common and the Signal is in spacing condition when the signal is more than +3 Volts w.r.t to the circuit. The region between +- 3 Volts is said to be the ๐ญ๐ซ๐š๐ง๐ฌ๐ข๐ญ๐ข๐จ๐ง ๐ซ๐ž๐ ๐ข๐จ๐ง. The signal state is undefined when the signal is in the transition state.

ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย The RS 232 does not use a clock signal. So when do the devices know which bit is being delivered when or w๐ฐ๐ก๐ข๐œ๐ก ๐›๐ข๐ญ ๐ญ๐จ ๐ซ๐ž๐š๐ ๐ฐ๐ก๐ž๐ง?

ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย The devices should agree on the data rate or popularly known as ๐๐š๐ฎ๐ ๐‘๐š๐ญ๐ž.

ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย Baud= Symbols/Second

ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย Commonly used Baud rates are 4800,9600,38400,57600,115200…

ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย If we select 9600 as the baud rate, then we get 1/9600 i.e ~0.000104167 i.e 1 bit every 4 microseconds

ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย The first bit is the start bit i.e 1. The next 8 bits are data bits.

The least significant bit is the first.

After transitions of the last bit, the signal stays low until the next bit press. It does so as it requires a minimum amount of ideal time for transmission between 2 characters.

Although there are many new protocols, RS-232 is still widely used in many industries.

How was your experience with RS-232? Did you use it?

#embedded #embeddedsystems #cprogramming #protocols #rs232 #learning #reach #Tia232 #embeddedprotocols

Image Soruce: EngineersGarage
Inforamtion: Ben Eaters Youtube and Wiki

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