Notes on configuration and operation
5.5 Connection monitoring, data buffering, acknowledgement
CP 1242-7 V2
42
Operating Instructions, 05/2014, C79000-G8976-C311-00
5.5.3
Frame buffer and acknowledgement
Data buffering when there is a connection abort ("Telecontrol")
If the parameter in the data block TCON_WDC is "RemoteWdcAddress" = DW#16#0, the
send frames are stored with a time stamp in the frame buffer of the CP in the following
situations:
When the connection to the telecontrol server is interrupted
If the connection monitoring time is exceeded
The next time a connection is established to the telecontrol server, the buffered frames are
sent to the relevant destination subscribers.
The frame buffer is a ring buffer: If the buffer capacity is exceeded the oldest frames are
discarded without a warning message.
The frame buffer is only deleted when the operating mode is changed or when the device is
switched off.
The maximum number of stored frames can be found in the section Performance data
(Page 11).
Monitoring and acknowledgement of send frames
The receipt of a frame is monitored and acknowledged in different ways. The mechanisms
differ depending on the recipients as follows:
Recipient: Telecontrol server
After processing the send job, DONE is set to 1 in the "TC_SEND" instruction.
If there is a connection abort or the send monitoring time is exceeded, the frame is
buffered and sent to the telecontrol server when the connection is re-established.
Receipt is acknowledged by a frame from the telecontrol server.
Recipient: CP 1242-7 GPRS V2 - "Telecontrol" mode
The frame is forwarded by the telecontrol server to the destination CP.
Receipt is acknowledged by a frame from the destination CP. DONE is only set to 1 in the
"TC_SEND" instruction after receiving the acknowledgement.
If there is a connection abort or the send monitoring time is exceeded, TC_SEND outputs
to the ERROR and STATUS condition codes. The sending of the frame is not
automatically repeated.
Recipient: CP 1242-7 GPRS V2 - "GPRS direct" mode
If the network interface acknowledges that the frame was sent successfully, it sends the
message "TC_SEND" DONE.
