Start/Stop bit? (1 Viewer)

[laurel18]

What is a start / stop bit? Is it just the starting and ending 0 or 1 of a character?

 

[brownsound]

stop and start bits are the bits placed on the front and end of a data blocks in asynchronous transmission. the start bit informs the recieving device that another character is on its way, while the stop bit tells the reciever that its finished sending and to wait for another start bit.
and i think they are bigger (double) than the normal bits so they dont get confused

hope that helps in some way

 

[laurel18]

yes...that makes sense. Thanks brownsound.

 

[mymuse]

just a question, in the textbook, it says asynchronous transmission has a start, stop and a parity bit. what's the parity bit used for?

thanks

 

[falcon07]

The parity bit is used for error checking in the data block. Parity can either be odd or even.

Eg.

Even parity
Data block.....................parity bit
01100110....................... 0

Making the sum of all the bits even.

If there is an odd number of errors in the transmission the sum of all the bits won't be even. An error will be detected, resulting in retransmission.

 

[seremify007]

The one thing I've always wondered is... why couldn't they standardize the parity bit as even OR odd? Why give the choice?!

Warning to students doing HSC: Make sure you understand how these bits work because you could potentially be asked to deconstruct an incorrect transmission!