Basic Principles of Serial Data Transmission
2.4 Data Transmission with the ASCII Driver
Point-to-point connection CP 440 Installation and Parameter Assignment
34
Manual, 09/2007, A5E00057742-03
End Criterion "Expiration of Character Delay Time"
When data is received, the end of the message frame is recognized when the character
delay time expires. The received data is accepted from the CPU.
In this case the character delay time must be set such that it easily expires between two
consecutive message frames. But it should be long enough so that the end of the message
frame is not falsely identified whenever the partner in the link takes a send pause within a
message frame.
The figure below illustrates a receive operation with the end criterion "expiry of character
delay time".
:DLWLQJIRU
FKDUDFWHU
&KDUDFWHU
DUULYHG
&KDUDFWHUUHFHLYHG
ZLWKFKDUDFWHU
GHOD\WLPHPRQLWRULQJ
0HVVDJHIUDPH
HQWHUHGLQUHFHLYH
EXIIHU
(UURUHQWHUHGLQWKH
67$786RXWSXWRI
WKH)%
:DLWLQJIRUFKDUDFWHU
GHOD\WLPH5HFHLYHG
FKDUDFWHUVGLVFDUGHG
(UURUZKHQUHFHLYLQJQRWD
FKDUDFWHUGHOD\WLPHHUURU
0HVVDJHIUDPH
FRPSOHWHFKDUDFWHU
GHOD\WLPHH[SLUHG
0
H
V
V
D
J
HI
UD
P
HE
X
II
H
UH
G
(Q
GF
UL
WH
UL
R
QI
R
UP
H
V
V
D
J
HI
UD
P
HL
G
H
Q
WL
IL
H
GH
UU
R
UH
Q
WU
\I
R
OOR
Z
V
Figure 2-5
Sequence of Receive Operation with End Criterion "Expiration of Character Delay Time"
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