asynchronous data transfer

7/25/2019 Asynchronous Data Transfer

1/19

CS-A

ASYNCHRONOUS DATA

TRANSFERGuided By: Submitted By:

Mrs. Ru!"i B#!rtiy! N!$i% &um!r S#!rm!

R'"" %'.:()(*CS+,D(*

SHR /ASHNA/ NSTTUTE OF

TECHNO0OGY 1 SCENCE2 NDORE


2/19

NTRODUCTON


3/19

%tr'du3ti'%

Asynchronous data transfer between two

independent units requires that control signals

be transmitted between the communicating

units to indicate the time at which data is being

transmitted


4/19

T4' Asy%3#r'%'us D!t! Tr!%s5er Met#'ds

Str'be u"se:

A strobe pulse is supplied by one unit to indicate

the other unit when the transfer has to occur

H!%ds#!6i%7

A control signal is accompanied with each data being

transmitted to indicate the presence of data The

receiving unit responds with another control signal to

acknowledge receipt of the data


5/19

STROBE CONTRO0

Employs a single control line to time each

transfer

The strobe may be activated by either the

source or the destination unit


6/19

Source

Unit

Destination

Unit

D!t! bus

Str'be

Str'be

D!t!/!"id d!t!

!8 B"'36 di!7r!m

b8 Timi%7 di!7r!m

S'ur3e-%iti!ted Str'be 5'r D!t! Tr!%s5er


7/19

Desti%!ti'%-%iti!ted Str'be 5'r D!t! Tr!%s5er

Source

Unit

Destination

Unit

D!t! bus

Str'be

Str'be

D!t!/!"id d!t!

!8 B"'36 di!7r!m

b8 Timi%7 di!7r!m


8/19

HANDSHA&NG

Str'be Met#'ds

S'ur3e-%iti!ted

The source unit that initiates the transfer has no way of knowing whether

the destination unit has actually received data

Desti%!ti'%-%iti!ted

The destination unit that initiates the transfer no way of knowing whether

the source has actually placed the data on the bus

To solve this problem, the HANDHA!E method introduces a second

control signal to provide a "eplay to the unit that initiates the transfer


9/19

SOURCE-NTATED TRANSFER USNG

HANDSHA&E

B"'36 Di!7r!m

S'ur3e

u%itDesti%!ti'%

u%it

D!t! $!"id

D!t! bus

D!t! !33eted


10/19

Timi%7 Di!7r!m


11/19

Se9ue%3e '5 E$e%ts


12/19

Allows arbitrary delays from one state to the

ne#t

$ %ermits each unit to respond at its own data

transfer rate

$ The rate of transfer is determined by the

slower unit


13/19

DESTNATON-NTATED TRANSFER

USNG HANDSHA&E

B"'36 Di!7r!m

S'ur3e

u%itDesti%!ti'%

u%it

D!t! $!"id

D!t! bus

Re!dy 5'r D!t!


14/19

Timi%7 Di!7r!m


15/19

Se9ue%3e '5 E$e%ts


16/19

ASYNCHRONOUS SERA0

TRANSFER

The transfer of data between two units my be done in

parallel or serial&

'n parallel data transmission, total message is transmitted at

the same time& 'n serial data transmission, each bit in the

message is sent in sequence one at a time&

'n asynchronous transmission, binary information is sentonly when it is available and the line remains idle when

there is no information to be transmitted&


17/19

St!rt

bit

St'

bitC#!r!3ter bits

( ( ((

) ) ) )

ASYNCHRONOUS SERA0

TRANSFER


18/19

Asynchronous serial transmission is character

oriented&

Each character transmitter consists of a start bit,

character bits, and stop bits& The first bit is called

the start bit&

't is always a ) and is used to indicate the

beginning of a character& The last bit called the

stop bit is always a (&


19/19

T#e E%d

T#!%6 Y'u

asynchronous data transfer

Documents