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Redundant Field Device with Single Chassis

In this case the field device has a single chassis but uses two network interface cards for communications with the VIMs. Connect each network card to a separate isolated switch corresponding to the VIM. The IP address of these network cards must be consecutive, e.g., 10.22.6.50 and 10.22.6.51. No IP switching is expected or performed. Use RsLinx to configure static IP addresses of the ENBT cards.

VIM A will always communicate with the first IP address 10.22.6.50 and VIM B will always communicate with 10.22.6.51. If a VIM is in Standby, it will send a periodic “ping” to its assigned IP address. The ping allows the standby VIM to ensure that the communication path is valid. If the standby VIM cannot verify network path validity, an error message will be generated back to DeltaV indicating Standby problems and switchover will not be available. If the standby path is valid, user can command VIM switchover using DeltaV Diagnostics. Note that the “ping” is the Rockwell Echo Command 6, Function 0.

If the Active VIM loses communications and the Standby path is valid, the VIM will automatically request a switchover to its partner. The DeltaV controller verifies that the switchover is possible and then commands the currently Active VIM to go Standby, and at the same time commands the currently Standby VIM to go Active. Both VIMs maintain current DeltaV outputs. On switchover, the new Active VIM immediately starts scanning the field inputs to update its internal database.

The following illustrates the network for this level of redundancy:

Figure 1 - Redundant VIMs with single Logix Chassis

Scenario 1 Operating Conditions:

VIM A State

VIM B State

Redundancy State

Good

Good

VIM A stays active

Good

Bad

VIM A reports standby problems – switchover unavailable

Bad

Good

VIM A requests a switchover to VIM B

Bad Bad Report bad status to DeltaV dataset

Table 1 - Non-switching IP, VIM A Active

Scenario 2 Operating Conditions:

VIM A State

VIM B State

Redundancy State

Good

Good

VIM B stays active

Bad

Good

VIM B reports standby problems – switchover unavailable

Good

Bad

VIM B requests a switchover to VIM A

Bad Bad Report bad status to DeltaV dataset

Table 2 - Non-switching IP, VIM B Active