How to choose a NUT value?

nqn827 · Feb 8, 2011

Hi all,

Would someone please tell me if there is a "general" rule in choosing a Network Updated Time (NUT) for a RsLogix 5000 project?

TIA

Operaghost · Feb 8, 2011

What is the absolute fastest interval you require to get data exchanged between any two nodes on the network? That is what the NUT must be. No exchanges faster than the NUT are allowed.

OG

nqn827 · Feb 8, 2011

Hi,
Thank you for replying. Could you tell me if there is a "penalty" if one makes the NUT much faster than it should be?

Ken Roach · Feb 8, 2011

The principal drawbacks to a short NUT are:

1. Fewer nodes can transmit during a single NUT.
2. Less unscheduled bandwidth available.
3. Higher CPU utilization by the ControlNet bridges.

My habit is to use the default 5 ms NUT to start with and make it longer if I have a large number of nodes, or shorter if I need to tune up for some fast I/O.

The Plc Kid · Feb 8, 2011

Never seen the NUT time.

Is this just on controlnet or ethernet also?

How does this compare to RPI?

Ken Roach · Feb 8, 2011

Network Update Time (NUT) should really be called the Network Update Interval, but the common acronym is catchier, so the name stuck.

It's a general network setting in ControlNet that determines the cyclic timing of the network.

It doesn't exist in EtherNet/IP because Ethernet is stack-based and not time-based.

How to choose a NUT value?

nqn827

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