Siemens SIMATIC S7-400 CP 440 - Figure 2-5 Sequence of Receive Operation with End Criterion Expiration of Character Delay Time

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".
:DLWLQJIRU
FKDUDFWHU
&KDUDFWHU
DUULYHG
&KDUDFWHUUHFHLYHG
ZLWKFKDUDFWHU
GHOD\WLPHPRQLWRULQJ
0HVVDJHIUDPH
HQWHUHGLQUHFHLYH
EXIIHU
(UURUHQWHUHGLQWKH
67$786RXWSXWRI
WKH)%
:DLWLQJIRUFKDUDFWHU
GHOD\WLPH5HFHLYHG
FKDUDFWHUVGLVFDUGHG
(UURUZKHQUHFHLYLQJQRWD
FKDUDFWHUGHOD\WLPHHUURU
0HVVDJHIUDPH
FRPSOHWHFKDUDFWHU
GHOD\WLPHH[SLUHG
0HVVDJHIUDPHEXIIHUHG
(QGFULWHULRQIRUPHVVDJHIUDPHLGHQWLILHGHUURUHQWU\IROORZV
Figure 2-5 Sequence of Receive Operation with End Criterion "Expiration of Character Delay Time"
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