RS232 Serial Communication Protocol

 RS232 Communication Protocol. The term RS232 stands for "Recommended Standard 232" and it is a type of serial communication used for transmission of data normally in medium distances.

Serial communication – you are shooting a target using machine guns, where bullets reach one by one to the target.

Asynchronous Data Transfer – The mode in which the bits of data are not synchronized by a clock pulse. Clock pulse is a signal used for synchronization of operation in an electronic system.

Voltage Levels: RS232 also used as ground & 5V level. Binary 0 works with voltages up to +5V to +15Vdc. It is called as ‘ON’ or spacing (high voltage level) whereas Binary 1 works with voltages up to -5V to -15Vdc. It is called as ‘OFF’ or marking (low voltage level).

Received signal voltage level: Binary 0 works on the received signal voltages up to +3V to +13 Vdc & Binary 1 works with voltages up to -3V to -13 Vdc.

Line Impedances: The impedance of wires is up to 3 ohms to 7 ohms & the maximum cable length are 15 meters, but new maximum length in terms of capacitance per unit length.

Operation Voltage: The operation voltage will be 250v AC max.

Current Rating: The current rating will be 3 Amps max

main the use of this serial communication is used for the MAX232 ic it is came from dip packages

Generally, a microcontroller works at TTL of about 0 to 5V while a computer operates on the standards of RS232 like -25 to +25V. So interfacing a computer with a microcontroller is not possible without a MAX232 IC. For example; if you want to connect a PIC microcontroller to the serial pin of a laptop, then you must place MAX232IC among them.

• Pin-1(C1+): The positive terminal of a capacitor is connected to this pin
• Pin-2(Vs+): The capacitor’s positive leg is connected to it by grounding the negative leg.
• Pin-3(C1-): The negative pin of the capacitor is connected to this pin and the positive pin is connected to pin1
• Pin-4(C2+): The positive terminal of a capacitor is connected to this pin
• Pin-5(C2-): The negative terminal of a capacitor is connected where the positive terminal is connected to Pin4.
• Pin-6(Vs-): The negative terminal of a capacitor is connected to this pin & 5 volts is provided to the positive terminal of the capacitor.
• Pin-7(T2OUT): It provides the converted TTL signal in the form of RS-232. Here TTL signal can be obtained by T2IN Pin from the microcontroller and this pin is connected to Pin2 of DB-9 port of your computer like Rxd.
• Pin-8(R2IN): This Pin gets the signal of RS-232 like an input & provides the changed signal in the form of TTL on the R2OUT pin. This pin is connected to DB9 Port’s Txd pin, which is Pin3.
• Pin-9(R2OUT): It provides the signal changed within TTL form. The signal is received from Pc at R1In Pin. Connect this pin to your module (TTL) Rxd pin which receives the signal.
• Pin-10(T2IN): This pin gets transmitted signal from microcontroller & gives the changed RS-232 signal over T2OUT pin. Here, the signal can be transmitted from the microcontroller serial port’s txd pin. This pin can be connected to your Txd pin of the module.
• Pin-11(T1IN): This pin works like a T2IN.
• Pin-12(R1OUT): This pin works like an R2OUT.
• Pin-13(R1IN): This pin works like an R2IN.
• Pin-14(T1OUT): This pin works like aT2OUT.
• Pin-15(GND): This pin is a GND pin.
• Pin-16(VCC): This pin is a voltage supply pin where 5V is provided to this pin.

finally successfully simulated rs232 protocol in proteus