DNet remote i/o frequency response

I've spent hours looking on the rs website and more hours loading the knowledgebase cds (same as website) and now I'm here again. Does anyone know where I can find the maximum frequency that a 1790D digital input can respond to and whether that may relate to the size of the network. The input will be a flow meter with 50% duty cycle at a maximum of 10Hz. I figured that in the worst case I could set the module to cos and gate the input so that it only sees the pulses when the system needs to count them (just for purging the plant at product changeovers) so as not to keep the network permanently busy. Or have I misinterpreted cos as interrupt? Worst case is lower the resolution -not the end of the world- but I'd still like to find that spec...

Thank you.

The answer is "it depends".

A typical DeviceNet network cannot accurately count pulses that are shorter than about 20 milliseconds.

I say "typical" because there's so much variation in how you can set up a DeviceNet; you could have 5 nodes, or 55 nodes. You could be running at 125, 250, or 500 kb/s. You could have a bunch of tiny E3+ overloads or massive 1794-ADN adapters.

What is the network scanner ? The RPI rate of the scanner module's connection to the backplane matters, as do the available Inter-Scan Delay settings.

One way you could accurately measure the performance of your network is to use the Scan Count value in the Input tags; perform a GSV to get the CST clock value on two subsequent captures of the Scan Count, and use that to calculate the microseconds betwen the two subsequent scans.

50% duty cycle at 10 Hz is 50 milliseconds, and I like to scan at least twice per input to avoid getting bitten by the Nyquist-Shannon Sampling Theorem.

There are some I/O blocks, including 1790 CompactBlock, that support DeviceLogix, which I have used to accurately count pulses up to 500 Hz. The "LDX" light-duty blocks do not have this feature.