Waiting for
character
Character
arrived
Character received
with character
delay time monitoring
Message frame
entered in receive
buffer
Error entered in the
STATUS output of
the FB.
Waiting for character
delay time. Received
characters discarded
Error when receiving (not a
character delay time error)
Message frame
complete (character
delay time expired)
Message frame buffered
End criterion for message frame identified, error entry follows
Figure 2-5 Sequence of Receive Operation with End Criterion "Expiration of Character Delay Time"
End Criterion End-of-Text Character
When data is received, the end of the message frame is recognized when the congured end-of-
text character(s) arrive. The following options are available:
• One end-of-text character
• Two end-of-text characters, 1st and 2nd end-of-text characters
• Two end-of-text characters, 1st or 2nd end-of-text character
The received data including the end-of-text character(s) is accepted from the CPU.
If the end-of-text character is missing in the received data, the character delay time elapses
during reception and results in a termination of the frame. The character delay time is used in
this instance as the monitoring time. An error message is issued and the message frame
fragment is discarded.
Basic Principles of Serial Data Transmission
2.4 Data Transmission with the ASCII Driver
Point-to-point connection CP 440 Installation and Parameter Assignment
Equipment Manual, 03/2022, A5E00057742-AE 27
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