what is RS-232?

RS-232 connector

why we need it?

we always need to communication between peripheral device and computer.there are two ways of communication.

1.serial communication.

• serial communication one bit transmit at time.
• it's used for long distance.
• telephone line we used serial communication.
• less expensive then parallel

2.parallel communication.

• in this 8 bits are transmitted at time.
• its used for short distance.
• costly then serial communication.

 figure

Rs-232 standards.

• to allow data communication between two different manufacture equipment we need RS232 standard developed by EIA in 1960.
• RS 232 widely used standard I/O interfacing standards. 
• RS 232 is used data communication between data terminal equipment(i.e modem,printer,display screen) (DTE )and data communication equipment(i.e computer.)(DCE).
• today RS-232 technology replace by USB. 

 

 RS-232 connector:

there are two types of connector.

1.DB9 connector (9 pins).

2.DB 25 connector(25 pins).

DB9 CONNECTOR

 

DB25 CONNECTOR:

specification of RS-232 standards:
transmitted signal:
voltage level:

• Binary 0: +5 to +15 Vdc
• Binary 1: -5 to -15 Vdc

received signal:

voltage level:

• Binary 0: +3 to +13 Vdc
• Binary 1: -3 to -13 Vdc

DATA FORMAT:

• Start bit: Binary 0
• Data: 5, 6, 7 or 8 bits
• Parity: Odd, even, mark or space
• Stop bit: Binary 1