What Is A Serial Communication?
What Is A Serial Communication?
What Is A Serial Communication?
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.
Synchronous Data Transfer – The mode in which the bits of data are synchronized
by a clock pulse.
Characteristics of Serial Communication:
What is RS232?
RS232C “Recommended Standard 232C” is the recent version of Standard 25 pin
whereas, RS232D which is of 22 pins. In new PC’s male D-type which is of 9 pins.
RS232 is a standard protocol used for serial communication, it is used for connecting
computer and its peripheral devices to allow serial data exchange between them. As it
obtains the voltage for the path used for the data exchange between the devices. It is used
in serial communication up to 50 feet with the rate of 1.492kbps. As EIA defines, the RS232
is used for connecting Data Transmission Equipment (DTE) and Data Communication
Equipment (DCE).
RS232 protocol
Electrical Specifications
Let us discuss the electrical specifications of RS232 given below:
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.
Dielectric withstanding voltage: 1000 VAC min.
Slew Rate: The rate of change of signal levels is termed as Slew Rate. With its slew
rate is up to 30 V/microsecond and the maximum bitrate will be 20 kbps.
TXD TRANSMITTER
RXD RECEIVER
GND GROUND
For example: The signals set to logic 1, i.e., -12V. The data transmission starts from next
bit and to inform this, DTE sends start bit to DCE. The start bit is always ‘0’, i.e., +12 V &
next 5 to 9 characters is data bits. If we use parity bit, then 8 bits data can be transmitted
whereas if parity doesn’t use, then 9 bits are being transmitted. The stop bits are sent by the
transmitter whose values are 1, 1.5 or 2 bits after the data transmission.
Mechanical Specification
For mechanical specifications, we have to study about two types of connectors that is DB-
25 and DB-9. In DB-25, there are 25 pins available which are used for many of the
applications, but some of the applications didn’t use the whole 25 pins. So, the 9 pin
connector is made for the convenience of the devices and equipments.
Now, here we are discussing the DB-9 pin connector which is used for connection between
microcontrollers and connector. These are of two types: Male Connector (DTE) & Female
Connector (DCE). There are 5 pins on the top row and 4 pins in the bottom row. It is often
called DE-9 or D-type connector.
PIN
Pin Name Pin Description
No.