Manual VIPA CPU 21x Chapter 5 Deployment CPU 21x-2BT02 with H1 / TCP/IP
HB103E - Rev. 05/45 5-37
The TCP/IP protocol stack has a global buffer pool where the receive and
transmit buffers are located. This is where system collisions can occur if:
• Data for a receive job is not collected. After a period of time a lack of
resources will occur and the other connections will terminate
themselves.
It is only possible to re-establish proper communications when the
receive buffers of this connection have been released (connection
terminated) or when the data has been retrieved by means of RECEIVE.
• one or more cyclic stations place a load on a CP. When resource
bottlenecks are encountered, the CP can also initiate the termination of
connections.
• A station transmits two or more messages and the receiver did not have a
chance to accept them. Then the reception of the unknown data type
would cause collisions in the receiver. However, the CP prevents this. The
PLC application requires a defined size for the reception of data and the
wildcard length is not permitted. The size of the receive block of Prio1 -
RECEIVE jobs is defined implicitly by the pre-defined block size (16, 32,
64, 128, 256, 512Byte).
• VIPA recommends the use of acknowledgment messages on the user
level to ensure that data transfers are one hundred percent safe.
• Please regard, that the Port 7777 is used by WinNCS for
communication. This may not be occupied by other applications!
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