Serial communication adapters provide one or more serial ports to a host computer. They interface with the host computer via a data bus and add RS232, RS422, RS485 and/or other types of serial ports. RS232 is a serial communication standard that provides asynchronous communication capabilities with hardware flow control, software flow control, and parity checking. Most gears, instruments, and digital communication devices are equipped with an RS232 interface. The typical transmission speed for RS232 is 9600 bps at 15 m. RS422 is a serial communication protocol that supports multi-point connections and provides longer transmission distances than RS232. The maximum transmission distance for RS422 is 1.2 km at 110 kbps. RS485 is similar to the RS232 standard, but is actually an enhanced version of RS422. Typically, RS485 is used in applications that require the use of a single controller with multiple devices. Other protocols for serial communication adapters include inter-integrated circuit (I2C), serial peripheral interface (SPI), and Microwire® , a registered trademark of National Semiconductor Corporation.
