Computer Link with 3964(R) Transmission Protocol S5-95U, Second Serial Interface
3.6 The 3964(R) Transmission Protocol
The following explanations are not required for starting up the S5-95U. The protocol will be
described simply for the sake of explaining the DB1 parameter settings (e.g. mode number, data
format Table 3-4, 3-6).
Unlike protocol-free data transmission procedures, the 3964(R) procedure requires a protocol. This
means that the actual data to be transmitted must be enclosed between two control characters.
The 3964(R) driver ensures comparatively safe data transmission since the receiver must first signal
its readiness to receive to the transmitter (connection buildup) and confirm receipt of data after data
transmission. The 2964R transmission protocol offers an even higher degree of safety by sending an
additional block check character.
The 3964(R) driver interprets the following control characters:
• DLE (10
H
) Data Link Escape
• STX (02
H
) Start of Text
• NAK (15
H
) Negative Acknowledgement
• ETX (03
H
) End of Text
During parameter assignment, you may also decide whether data frames are to be sent with or
without block check characters. Block check characters (BCC) increase the safety of data
transmission. Depending on whether you wish to transmit data with or without block check
characters, the 3964R or 3964 transmission procedure should be used.
• Data transmission with block check characters: 3964R
• Data transmission without block check characters: 3964
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EWA 4NEB 812 6095-02
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