Reflective Memory VIs
Some of the Advanced Read VIs use reflective memory to return status and data information to the controller. Unlike the trajectory control VIs that also return this information, these specialized VIs read status and data information from the register and send it back in a much higher response time.
These VIs should not be used for event checking. Only use the information returned by these VIs for display purposes. This is because the tradeoff for significantly faster response time is that these VIs are not serialized with other operations. VIs that return data information are read from a register on the controller and refreshed every 5 ms. VIs that return status information are refreshed as soon as possible. This configuration makes the data and status information quickly accessible—in about 40 µs as opposed to > 2 ms with the trajectory control VIs. However, this also means that you can read status information sooner than the VI has time to execute. For example, a call to Start Motion followed immediately by a call to the move complete attribute of the Read Execution Status VI may return a True value because the Start Motion VI may not have started before the move complete status information is returned.
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Note VIs using reflective memory are not supported by the NI SoftMotion Controller. |
The following table lists the VIs using reflective memory, which controller has reflective memory support, and which attributes use reflective memory, if applicable:
| Function | 7330 | 7340 | 7350 | 7390 |
|---|---|---|---|---|
| Read All Axis Data | — | — | Y | Y |
| Read All Axis Status | — | — | Y | Y |
| Read Axis Data (all attributes) | — | — | Y | Y |
| Read Axis Status (all attributes) | — | — | Y | Y |
| Read Capture Compare Data Captured Position Position Capture Occurred Position Compare Occurred |
— — — |
— — — |
N Y Y |
N Y Y |
| Read Coordinate Data (all attributes) | — | — | Y | Y |
| Read Coordinate Status (all attributes) | — | — | Y | Y |
| Read Coordinate Position (all attributes) | — | — | Y | Y |
| Read Digital I/O Data Output Active State Input Active State Output Active Input Active Configure As Input |
N N N N N |
N N N N N |
N N Y Y N |
N N Y Y — |
| Read Encoder Data (all attributes) | — | — | Y | Y |
| Read Motion I/O Data Forward Limit Active Reverse Limit Active Forward Software Limit Active Reverse Software Limit Active Home Input Active Inhibit-In Active In-Position Active Drive Ready Active Inhibit-Out Active |
N N N N N N N N N |
N N N N N N N N N |
Y Y Y Y Y N N N N |
Y Y Y Y Y N N N N |