SELECT and OPERATE

It is possible to have separate SELECT and OPERATE operations for binary outputs (BO) and analog outputs (AO).

The timeout value for how soon an OPERATE is needed after a SELECT is set in the RTU. Therefore, the default Citect.ini parameters MaxOperateDelayDefault and MaxOperateDelay (per unit) need to be changed to match this time.

Because this time is used to stall any polls for the unit while a SELECT[_ONLY] is pending. This is because the DNP protocol requires that the next request after a SELECT[_ONLY] is an OPERATE.

Be reminded that only one SELECT/OPERATE sequence can be done at a time on a single RTU. Multiple SELECTs cannot be done at once. This is a DNP3 limitation.

Users should display the WRITE PENDING bit and the WRITE FAIL bit to verify correct operation. Typically, if you send an OPERATE after the max. delay time, you will see the WRITE FAIL tag light up.

A SELECT can be manually canceled by writing to the BO/AOx.CancelSel tag. This will clear all other status bits for SELECT/OPERATE.

Forced Integrity or Event polls should not occur while a SELECT[_ONLY] command is pending. The software will automatically delay regular scheduled polling help ensure no poll occurs while a SELECT[_ONLY] is pending.

Status bits BO/AOx.<WrtPend,WrtFail,SelPend> are available to provide user feedback on the SELECT/OPERATE sequence.

Note: In an earlier version of the DNPR driver, the SELECT command was effectively a SELECT and OPERATE (automatic). This remains unchanged. Where you see an address with ".Select.", this will be a SELECT and OPERATE. For a pure select only, the address needs to be ".SelectOnly".