YOKOGAWA Vnet/IP, Technical Information

Page: 20 / 70

1. Overview of Vnet/IP
1-10
TI 30A10A05-01E
n
Redundant CPUs in Vnet/IP stations
The duplexed FCSs, duplexed SCSs, and duplexed V net routers have two CPUs. Each of the
two CPUs is connected to layer 2 switches in a dual-redundant Vnet/IP.
As mentioned earlier, a Vnet/IP station stores information of other stations that are on
Vnet/IP. This includes information about CPU control rights. The sending station uses the control
rights information of the receiving station to determine the path to take for sending the control
information, and the CPU module to which the information is sent.
In the following figure, station A determines that CPU2 has the control rights for station B, and
therefore communicates with station B CPU2 through the layer 2 switch for bus 1. On the other
hand, CPU1 has the control rights for station C. However, a communication error occurs in the
path between station C CPU1 and layer 2 switch for bus 1. Therefore, station A CPU1 and station
B CPU2 communicate with station C CPU1 through the layer 2 switch for bus 2.
010302E.ai
L2SW
CPU1
(Stand-by)
Bus 1 side
Bus 2 side
CPU2
(Control)
CPU1
(Control)
CPU2
(Stand-by)
CPU1
(Control)
CPU2
(Stand-by)
Station A Station B Station C
L2SW
Figure Transmission Path for Redundant CPUs
Aug.19,2011-00