1. Overview of Vnet/IP
1-12
TI 30A10A05-01E
The single line in the gures actually represents two communication lines of bus 1 and bus 2.
When the bus 1 cable fails, as in the gure (2), bus 1 switches to detour by the ring structure and
continue Vnet/IP communication.
As in the gure (3), when the L2SW “B” on the bus 1 fails, the bus 1 switches to detour by the ring
structure; however, the failure point (the communication to the Vnet/IP station connected to the
switch B) will not recover and the Vnet/IP communication switch to the bus 2.
By adopting the ring structure, reliability of the Vnet/IP communication increases.
In case both bus 1 and bus 2 break at the same time and the switching of the dual redundancy
bus and the ring structure take place simultaneously, the following phenomenon may rarely
occur.
• A system alarm of “Communication Error” may occur.
• HIS message(s) may be lost.
• Process data on face plates and graphics may be temporarily displayed as “asterisk.”
• Trend data may be temporarily lost.
Dec. 26, 2016-00
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