Serial channels provide a simple, low-cost means for communication amoung digital systems. Serial interfaces for microcomputer systems are described in Clements, Chapter 7. The format of asynchronous serial data is shown in Figure 57.
When data is not being sent, the serial link is said to be idle and is high (1 or mark). To indicate the commencement of the transmission of a byte (8 bits) of data, a start bit is sent (0 or space) for one baud period (the baud rate indicates the bit rate here). The 8 data bits then follow for the next 8 baud periods. (The byte often consists of 7 data bits with the eighth bit being a parity bit for error correction.) The transmission is terminated by a 1 for one baud period. After this, other bytes can be sent in turn.
ANU Engineering - ENGN3213
