1.1 SERIAL DATA TRANSFER
• A single communication line links two computers, and allows communications one bit at a time.
• Typically strings are passed to and from a terminal, modem, mouse, etc.
• Each string is broken up and each byte is sent one at a time.
• Each byte is sent one bit at a time with the various framing options,
- A popular communication port found on almost all computer hardware, regardless of age.
- Can be robust in an industrial environment
- Standards are very clearly defined
• Speeds of 110, 150, 300, 600, 1200, 2400, 4800, 9600, 12000, 19200 baud (bits per second)
• Can use as few as three wires for connection, or more as advanced handshaking lines are required.
• Specialized chips, and modems are commercially available for using this interface
• Popular standards are RS (Recommended Standard)-XXX published by the Electronics Industries Association
- RS-232 - available on almost all computers
- RS-422 - a popular industrial standard which can be noise resistant then RS-232