How can I write to a discrete output (DO) point on a ROC?

You need to configure a ROC Plus Numeric Point with the correct Type, Location, and Parameter. The point has to have its Control aggregate enabled.

Details about the configuration of a DO point in a ROC, such as whether the DOUT type is latched, toggle, time duration or TDO toggle, and so on, are beyond the scope of this guide. However, assuming that you have a ROC with a DO that you have configured to your liking using ROCLINK 800 software, you can set the EU Value parameter, which is of type FP, by configuring a ROC Plus Numeric Point with the correct TLP and calling the Control method on the point.

The Type for a DO point is 102 and the EU value Parameter is 20. The Location is hardware dependent.

For further information, see ROC Plus Numeric Point.