Communication

• In serial transmission, the data is sent one bit at a time across a single wire
• In parallel transmission, multiple bits are sent at the same time across multiple wires running parallel to each other
• Individual wires will have different properties which can create skew - bits will travel at slightly different speeds and thus could arrive in the incorrect order
• Parallel transmission is mostly used for distances less than 2m, in integrated circuits and RAM. Serial is much more reliable over long distances
• Serial tends to be cheaper due to less complexity with cabling and connections
• Parallel may suffer from crosstalk, where interference between wires corrupts data, and this worsens at higher frequencies. Serial can operate at higher frequencies and thus higher speeds without interference
• In synchronous transmission, data is transferred at regular intervals controlled by clock pulses. Useful for time-sensitive data like video calls
• In asynchronous transmission data is sent as soon as it is ready
• Asynchronous transmission makes use of start and stop bits, to inform the computer where the start and end of each byte of data is. The stop bit must be opposite to the start bit
• Latency is the time delay between a component sending data and that data being received and acted upon
• A protocol is a set of rules outlining how devices should communicate, such as transmission speed and error checking method. Two devices can communicate if they use the same protocol
• Bit rate is the number of bits transferred per second
• Baud rate is the number of times the signal changes per second
• Bit rate and baud rate will be the same if only one bit is sent per signal for example a fixed high and low voltage encoding for 1 or 0
• Bit rate = baud rate * number of bits per signal
• Bandwidth is the maximum capacity of data of a communication channel
• Bandwidth is often used to generally refer to the data transfer rate