Chapter 9 Deployment CPU 21xSER-1 Manual VIPA CPU 21x
9-4 HB103E - Rev. 05/45
The 3964R procedure controls the data transfer of a point-to-point link
between the CPU 21x SER-1 and a communication partner. The procedure
adds control characters to the message data during data transfer. These
control characters may be used by the communication partner to verify the
complete and error free receipt.
The procedure employs the following control characters:
• STX Start of Text
• DLE Data Link Escape
• ETX End of Text
• BCC Block Check Character
• NAK Negative Acknowledge
STX
DLE
Message-data
DLE
ETX
BCC
Monitor delayed acknowledgment
DLE
Monitor delayed acknowledgment
ctive partner
Passive partne
You may transfer a maximum of 255Byte per message.
Note!
When a DLE is transferred as part of the information it is repeated to
distinguish between data characters and DLE control characters that are
used to establish and to terminate the connection (DLE duplication). The
DLE duplication is reversed in the receiving station.
The 3964R procedure requires that a lower priority is assigned to the
communication partner. When communication partners issue simultaneous
send commands, the station with the lower priority will delay its send
command.
3964R
Procedure
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