We have existing Devicenet networks used with DeltaV Devicenet cards for motor drive control. We have found an error where when we lose communication to a drive on Devicenet for a given device, there is no indication back to the operator other than a bad status on feedback Devicenet signals, such as when we pull current draw back through Devicenet (we do not have any wired auxillary contact feedback for run confirm). Typically Device Control (DC) function blocks at our site have been set up to compare current draw feedback via Devicenet signal with a minimum value as for Run Confirm status.
DeltaV Books Online does provide some guidance on this ( see section Using Profibus DP, DeviceNet, AS-Interface and EIOC with DeltaV function blocks), but they seem to recommend using an output status to interlock the device, with an appropriate time delay considering for drive fault time, so as to not bump the drive when communication is re-established.
Rather than an interlock I am looking at implementing Devicenet communication status into the Run Confirm (i.e. F_IN_D1) of the Device Control (DC) block as I believe this will provide the same function (i.e. device will fail) if communication is lost, where the device will FAIL in DeltaV if feedback is lost to F_IN_D1 parameter of the DC block. This is based on an intended drive configuration that is set to stop if communication is lost as well (i.e. DeltaV status & VFD should both stop if Devicenet communication is lost).
My questions are(1) Any concern to do this using Run Confirm rather than as an interlock condition as recommended by Books Online (2)Which Parameter should I be looking at. I think I have several options. I could use (1) Diagnostics parameter Devicenet Device Ointeg parameter (2) Diagnostics parameter Devicenet Device Status parameter or (3) Amp AI module PV status not BAD which anecdotally has been a good indicator for lost Devicenet communication since the Amp DST comes back on Devicenet for the device.
Any recommendations on whether this can be done in Run Confirm (F_IN_D1_ of DC block rather than interlock, and which Diagnostics or status parameter is the best to use? I appreciate any suggestions you might have