Most modern computers are interconnected with other computers in one way or another, whether by a dialup connection or over a local area network (LAN). For interconnections that cover distances greater than a few meters, serial connections are economical. In serial communications, the information bits are sent one at a time over a single communications channel. This stands in contrast to parallel communications, where information is sent one byte (or word) at a time over eight or more communications channels between the machines.

As in all communications, the problem normally focuses on establishing ways for the receiver (meaning the destination computer) to interpret and decode correctly the transmitted information. Communications protocols are designed to facilitate this in serial communications; they are especially important in this case because the receiver must be able to process correctly each bit that it receives.

Protocol Functions

For serial communications to...