Asynchronous systems Flashcards
How do asynchronous systems maintain synchronicity?
By adding start / stop bits
In its basic form, how does the start stop transmission look?
Start bit, data bits, stop bits
Why do Asynchronous systems require an extra element?
To inform the receive terminal where a word begins and ends.
Do these systems require any linked timing device to maintain synchronicity ?
No
When no data is being transmitted, what state is the link between the transmit and receive terminals in?
It is in an idle state
How does a receive terminal determine when a data transmission has restarted ?
The start bit will be a different polarity than the stop bit
How do the start and stop bits differ
They have different polarities
What is the stop bit also called
The idle state
In asynchronous systems, are the clocks independent of each other, or are they linked together
They are independent of each other
Because the clocks are independent of each other, what can that cause ?
Drift or slippage may be caused within the data stream, causing a loss of synchronicity and corruption of the transmitted data
Where does the receive clock start it’s timings from?
It will start once it sees the leading edge of the first bit, then take its timing from the centre of each bit that follows
How often does the receive clock re sync?
On completion of each frame, before the next frame is sent
What are the advantages of asynchronous systems ?
They are relatively simple and cheap
What do asynchronous systems always require ?
An over head or additional bits, 2-3 per character
How do some systems reduce the over head
By sending larger blocks of data between the start and stop bits
