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Cable Length Discovery Uncertainty Factor

The detected cable length measured at discovery time has an uncertainty factor that can affect control latency.

For most systems, the uncertainty is small (+/-0.160 uS for an 8 node network) and is completely hidden when latency schedule is rounded up to N*drivePeriod. For these systems, the cable length uncertainty has no effect on control latency. However if a given system is close to the boundary between N and N+1 drivePeriods, even a tiny uncertainty can bump the latency by a full drivePeriod.

For these systems, one of the following additional measures should be taken:

 

Also, non-periodic nodes (RMBs) have no roundup and their latency is directly affected by cable length uncertainty, however the variation in such cases is minimal.

 

See Also:

MPISqNodeConfigControlLatency

Cable Length | Node Control Latency

 

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