Section 6 - Communication Methods

Sending and receiving data from one device to another

Within the CPU and between the CPU and it’s peripheral devices

• Serial • Parallel

Bits are sent via an interface one bit at a time over a single wire from the source to the destination

Several bits are sent simultaneously over a number of parallel wires

• Integrated circuits • RAM

An issue that occurs due to each individual wire in parallel data transmission having slightly different properties, meaning bits may travel at slightly different speeds

• Connectors are much smaller and simpler, reducing the associated costs • “Crosstalk” can create interference between parallel lines, resulting in corrupted data that must be retransmitted • Serial links are more reliable over long distances • Because of the lack of interference, serial transmission can operate at a much higher frequency and therefore result in a higher net data transfer

The speed at which data is transmitted serially

Bits per second

The rate at which the signal changes

baud rate * number of bits per signal

Only 2 voltage levels are used, representing 0 and 1. In this case the baud and bit rate are the same

The range of frequencies that a transmission medium can carry. The large the range, the greater the amount of data that can be transmitted in a fixed amount of time

Bits per second

The time delay between the moment that the first byte or packet is transmitted, and when it is received at its destination

A set of rules relating to communication between 2 devices

A particular pattern of bits that is represented by a signal

Where a clock is used to time when signals are sent. It is used within the busses of a computer’s processor in the fetch-execute cycle

For transmitting information in real-time systems

Where one byte at a time is sent, with each character being preceded by a start bit and followed by a stop bit. The start bit alerts the receiving device and synchronises the clock inside the receiver ready to receive the character