Fallback Strategy

Quantum S908 Adapter Module Fallback

In some instances, the 140CRA31908 module can lose I/O connections for a period longer than the configured hold up time. During the hold up, the module tries to get IP and configuration parameters from the CPU. If the module does not obtain those parameters, it gets these results:

inputs: retain last known values
outputs: set to fallback

Configure both hold up times:

One for the Quantum S908 remote drop on the EIO Bus (drop with 140CRA31908 adapter module). Set the hold up time value on the Control Expert Parameter tab.
One for the Remote IO Quantum drop on the RIO Bus (drop with 140CRA93•00 adapter module). Set the hold up time value (multiple of 100 ms) on the Control Expert Configuration tab. Default values are 300 ms for standalone Quantum S908 configuration and 1200 ms for redundant Quantum S908 configuration.

NOTE: The hold up time for the Remote IO Quantum drop starts only after the hold up time for the Quantum S908 remote drop has expired. As a consequence, the IOs over the S908 network follow the fallback strategy after the time equal to Quantum S908 remote drop hold up time + Remote IO Quantum Drop hold up time.

Fallback Strategy

Adopt a fallback strategy:

outputs: Configure a value for each channel in the output modules or accept the fallback values.
inputs: You cannot configure fallback values for input modules.

Behavior	Description
PLC in STOP	inputs: When the M580 PLC is in STOP, the S908 inputs are inhibited. When the PLC returns to RUN, it reads the remote drop inputs before it solves the logic. outputs: When the M580 PLC is in STOP, the S908 outputs retain the last values or the fallback values (according to the configuration).
The RIO master is not healthy.	If the RIO master is not healthy when a single 140CRA31908 module is configured and the CPU is running, these items are true: inputs: All inputs that are configured over the S908 network are set to 0. outputs: All outputs are set to fallback values.
The remote drop is not healthy.	For both single and redundant S908 networks, the loss of communication between a remote drop and its master 140CRP93•00 module has these results: inputs: All inputs are reset. outputs: All outputs are set to fallback values.
The 140CRA31908 module is not connected.	standalone: These events occur when the 140CRA31908 module loses its EtherNet/IP connection in a standalone configuration: inputs: All inputs that are configured over the S908 network are set to 0. outputs: All outputs are set to fallback values. redundant: These events occur when the 140CRA31908 module loses its EtherNet/IP connection in a redundant configuration: No CPU switchover occurs.
The CPU is running.	EtherNet/IP or S908 networks: When the CPU is running, you cannot use system words %SW8 or %SW9 to inhibit the input or output over these networks. When the CPU is running, you cannot apply fallback values in these networks.

NOTE: When an I/O error is detected over the S908 network, %S10 and %S117 are set to 0. The IO LEDs on the CPU and 140CRA31908 are on.