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Communications Capabilities
Sending and Receiving Frames
•
Each character whose value is 10
does not interpret it as the control character for connection buildup. The receiver enters only
one of the two characters in its Receive buffer.
•
The receiver monitors the time that elapses between transmission of two consecutive
characters. If it exceeds the specified character delay time (ZVZ), the receiver sends a NAK and
waits the amount of time defined in word 6 of the parameter list for the frame to be
retransmitted. (Character delay time: Word 3 in the parameter list).
•
The following occurs when the receiver's Receive buffer is full before the transmitter has
initiated a connection cleardown:
-
receiving continues until the connection has been cleared down
-
the receiver subsequently transmits the NAK control character
-
the error is flagged in the CBR.
•
If the receiver sends a NAK character to the transmitter while transmission is in progress, the
transmitter aborts the data transfer and retransmits the entire frame, beginning with the first
character.
•
If the receiver sends a character other than NAK while transmission is in progress, the
transmitter ignores it and continues its transmission
•
The receiver reacts to a transmission error (character lost, bad frame, parity error) as follows:
-
Reception continues until the connection is cleared down
-
NAK is then transmitted
-
If an attempt to transmit is still possible (word 8 of the parameter list), the receiver waits
for the frame to be retried. How long the receiver waits depends on the frame delay time
(word 6 in the parameter list).
The receiver aborts transmission and reports an error in CBR
-
if the data block could not be received at the last send attempt
or
-
if the sender does not start sending within the block waiting time.
•
The "BREAK" signal causes the transmitter to
-
abort the current transmission
-
send NAK
-
flag an error in the CBS.
•
If a message frame is not accepted (no positive acknowledgement) after the set number of
tries to erect or tries to send, the sender responds by sending a NAK.
12-44
(DLE) is transmitted twice in succession so that the receiver
H
S5-115U Manual
EWA 4NEB 811 6130-02b
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