There should be additional error messages that have more detail on exactly why the 1030 error fired.
General rule for working with RSI: add a MONITOR object, and record the realtime data during your test runs. The data can then be exported to chart in Excel or MatLab or your software of choice. It's really about the only way to see what happened inside an RSI object.
So one thing that I am wondering is the robot is in motion (being controlled via a motion controller through the RSI) and while the robot is in motion I try to set a Digital output on and another digital output off. Does the robot need to not be in motion while I set a digital output or can the robot be in motion and have the digital outputs changed concurrently?
How are you setting the outputs? From an RSI object, or something in KRL?
As long as the RSI object is running, it doesn't matter if the robot is moving or not. You can build RSI containers that have no motion objects at all, and they still work.
Also, I read somewhere that the cause is: "Sensor error that requires ramp-down braking. Depends on the sensor concerned." How do I do ramp-down braking and on what do I do the ramp-down braking for.
You don't. Ramp-down braking is the robot's natural reaction to an error of this level. The manual is simply describing it -- "requires" doesn't mean you're required to do it, it means that there's no way around it -- if this fault occurs, the robot will do this.
Ramp-down braking can be either Stop 1 or Stop 2, depending on the severity of the error. Braking without a ramp-down (panic stop) is Stop 0, where the robot instantly kills power to the motors and slams the brakes on, with no regard to maintaining path or damage to the hardware.
E-Stops are usually Stop 1 (a fast ramp-down braking with a low priority on path maintenance). Stop 0s are usually reserved for events like "lost communications with servo mid-motion", and other potentially-catastrophic events.
