Bus Communication Speeds

Data must be transmitted at high speed in order to make digital communication practical. The speed of these signal is referred to as the data rate (formerly baud rate). Depending on the type of bus network used, data can be transmitted from 9600 bits per second (9.6k/bps) to 500K bits per second (500K/bps).

Current fiber optic systems can transmit and receive data up to 22.5 M/bps.

Depending on the system requirements, bus networks communicate at different speeds. Systems such as powertrain control require a large amount of data to be transferred due to constantly changing values such as RPM, road speed and throttle position etc. Therefore the CAN-Bus (or PT-CAN) operates at 500 K/bps.

Faster communication speeds are required for video and audio signals. Therefore, the MOST-Bus is designed to handle these needs and can communicate at 22.5 M/bps.

To accurately describe the speed of data transmission the term "bps" (bit per second) is used. This is not to be confused with baud rate. Baud rate refers to the rate that a change of state occurs on a signal line. Any voltage change on the signal line is a change of state, but this does not relate directly to the amount of bits per second. In other words, more that one bit can be transferred per baud. This is dependent upon the type of communication protocol.

In this course, data communication speed will be referred to as bit per second (bps). A "bit" is an abbreviation for binary digit. A bit is the smallest information unit that a computer can process. A series of 8 bits make up one byte and a series of bytes make up a bus telegram message.