Synchronous Transmission:
The type of transmission where data are sent block (frame) by block without any
regular interval is called synchronous transmission.
|
8 bit
flag
|
Control
field
|
Data
field
|
Control
field
|
8 bit
flag
|
Figure:
Character format of synchronous transmission.
The block may be many bits in length to prevent
timing drift between transmitter and receiver there clock has to be
synchronized... That’s why Manchester or differential Manchester encoding
technique is used here.
Features:
(i)
Data are sent block by block.
(ii)
Data has to be sent after a specific time period.
(iii)
The interval between to sending block is equal.
(iv)
There is no start or stop bit.
(v)
A primary storage is needed to store the sending data.
(vi)
It is more expensive.
(vii)
It is more efficient.
Asynchronous Transmission: This type of transmission here data are sent
character by character without transmission.
|
stop
bit
|
|
|
|
|
stop
bit
|
Figure:
Character format of asynchronous Transmission.
The strategy of type of transmission is to avoid the
timing problem but not sending long uninterrupted series of data.
Features:
(i) Data are sent
character by character.
(ii) Data can be
sent any time.
(iii) The time
interval between to sending character is not equal.
(iv) There exists a
start and stop bit before and after every character.
(v) No primary
storage is needed here.
(vi) It is less
expensive.
(vii) It is less
efficient.
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