Primary difference between RS-232, RS-422 & RS-485 serial interfaces
RS-232 is the most common serial interface and ships as a standard component on most Windows-compatible desktop computers. RS-232 only allows for one transmitter and one receiver on each line. It also uses a Full-Duplex transmission method. Some RS-232 boards support baud rates up to 1 Mbit/s, but most devices are limited to 115.2 kbits/s.
Note that RS-422/RS-485 interface is not available on most IBM PCs.
RS-422 (EIA RS-422-A Standard) is the serial connection used on Apple computers. It provides a mechanism for transmitting data up to 10 Mbits/s. RS-422 sends each signal using two wires to increase the maximum baud rate and cable length. RS-422 is also specified for multi-drop applications where only one transmitter is connected to, and transmits on, a bus of up to 10 receivers.
RS-485 is a superset of RS-422 and expands on the capabilities. RS-485 was made to address the multi-drop limitation of RS-422, allowing up to 32 devices to communicate through the same data line. Any of the slave devices on an RS-485 bus can communicate with any other 32 slave devices without going through a master device. Since RS-422 is a subset of RS-485, all RS-422 devices may be controlled by RS-485.
Both protocols have multidrop capability, but RS-485 allows up to 32 devices and RS-422 has a limit of 10. For both communication protocols, you should provide your own termination.
The following table compares mode of operation, total number of drivers and receivers, maximum cable length, and maximum data rate.
RS-232 is the most common serial interface and ships as a standard component on most Windows-compatible desktop computers. RS-232 only allows for one transmitter and one receiver on each line. It also uses a Full-Duplex transmission method. Some RS-232 boards support baud rates up to 1 Mbit/s, but most devices are limited to 115.2 kbits/s.
Note that RS-422/RS-485 interface is not available on most IBM PCs.
RS-422 (EIA RS-422-A Standard) is the serial connection used on Apple computers. It provides a mechanism for transmitting data up to 10 Mbits/s. RS-422 sends each signal using two wires to increase the maximum baud rate and cable length. RS-422 is also specified for multi-drop applications where only one transmitter is connected to, and transmits on, a bus of up to 10 receivers.
RS-485 is a superset of RS-422 and expands on the capabilities. RS-485 was made to address the multi-drop limitation of RS-422, allowing up to 32 devices to communicate through the same data line. Any of the slave devices on an RS-485 bus can communicate with any other 32 slave devices without going through a master device. Since RS-422 is a subset of RS-485, all RS-422 devices may be controlled by RS-485.
Both protocols have multidrop capability, but RS-485 allows up to 32 devices and RS-422 has a limit of 10. For both communication protocols, you should provide your own termination.
The following table compares mode of operation, total number of drivers and receivers, maximum cable length, and maximum data rate.
Serial communication Interface is used for communication between development board and a computer or with other devices.The development kits have atleast one serial port known as UART or USART.It communicates on digital pins 0 (RX) and 1 (TX) as well as with the computer via USB. Thus, if you use these functions, you cannot use pins 0 and 1 for digital input or output.This is a general mistake committed by beginners.
Don't connect these pins directly to an RS232 serial port; they operate at +/- 12V and can damage your development board.It will damage your development board.
Don't connect these pins directly to an RS232 serial port; they operate at +/- 12V and can damage your development board.It will damage your development board.