Synchronous and Asynchronous

Synchronous and Asynchronous transmission are two methods (protocols) of keeping data synchronised when transmitted.

Asynchronous data transmission

• Data is transmitted in discrete packets (usually 1 byte)
• Each packet of data is sent with control bits
• The control bits allow the receiver to know when the data starts and ends
• The control bits prevent the packets of data getting mixed up
• Packets are sent intermittently (they have uneven time intervals between them)
• Slower than synchronous

Synchronous data transmission

• A continuous stream of data
• The data is accompanied by timing signals (generated by an internal clock)
• The clock ensures the sender and receiver are in step with each other
• The receiver counts how many bits were sent over a period of time then reassembles them into bytes (multiple bytes sent at once)
• Timings have to be accurate as there are no control bits
• Faster than asynchronous

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