LCD Screen Editor: Using Fields with Multiple Write Locations

Overview

A write location is a register in the RMC that is changed when a new value is entered for a field. When a field is first made editable, it will automatically have a single write location that matches the Data to Display area in the field pane's Data tab. For most fields this is all that is required. However, editable integer fields can have more than one write location.

For example, suppose an Event Step sequence has two steps that each start a move. You want the speeds of each move to be the same, but you also want that speed to be editable from the LCD420. In this situation, you would first set up a field to display the first step's speed register. You would make this field editable and give it appropriate limits. Next, a second write location—specifically, the second step's speed register—will make editing this single field change the speed in both steps.

Write Location Limitations

There are several limitations to keep in mind when using multiple write locations:

The first item in the Write Locations list is always the same as the Data to Display area of the field pane's Data tab. That is, it is neither possible nor desirable to have the value displayed for a field not correlate to the value that is edited. Therefore, changing the Data to Display area will automatically change the first Write Locations list item, and similarly changing the first Write Locations list item will automatically change the Data to Display area.
When a value is entered in a field with multiple write locations, one value is written per control loop. For example, suppose a field writes to both Step 1 Speed and Step 2 Speed. When a value is entered in this field, the value will be first written to Step 1 Speed, and one control loop later (1 or 2 ms) will be written to Step 2 Speed. This is usually not important, but may be in some circumstances.
The RMC supports up to a total of 32 fields having more than one write location. That is, you can have as many editable fields as you want, except that only 32 of these fields can have more than one write location. The Edit Write Locations dialog box lists the total multi-location fields used. See the discussion below on this dialog box.
The RMC supports a total of 256 write locations among all multi-location fields. That is, the sum of all write locations of only those editable fields with more than one write location cannot exceed 256. The Edit Write Locations dialog box lists the total multi-location field locations used. See the discussion below on this dialog box.
Each editable field can have up to 128 total write locations. However, the total number of write locations of all multi-location fields still must be under the 256-location limit. The Edit Write Locations dialog box lists the total write locations for the field. See the discussion below on this dialog box.

Editing the Write Location List

The following procedures describe how to modify the Write Locations list.

To start editing the write locations list:

Ensure that the Data to Display area indicates an integer field that can be edited, and that the Editable check box on the field pane's Format tab is selected.
In the field pane, click the Data tab.
Under Write Locations, click Edit. This will open the Edit Write Locations dialog box.

To add a write location:

Open the Edit Write Locations dialog box as described above.
Under Write Locations, click New.

This command will be unavailable if any of the limits are exceeded. See the discussion below on checking that you have not exceeded a limit.

Under Location Detail, select the appropriate settings for the desired write location. See Data Tab Details for additional information on setting up these fields.

To remove a write location:

Open the Edit Write Locations dialog box as described above.
In the Write Locations list, select the write location you wish to remove.
Under Write Locations, click Remove.

This command will be unavailable if you only have one write location left. You must keep at least one write location.

To edit a write location:

Open the Edit Write Locations dialog box as described above.
In the Write Locations list, select the write location you wish to remove.
Under Location Detail, change the settings for this write location. See Data Tab Details for additional information on setting up these fields.

To check the write location limits:

Open the Edit Write Locations dialog box as described above.
You will find the three numerical limits in the following locations. Each limit takes the form "n of m (p)," where n is the number currently used, m is the maximum number allowed, and p is the percentage of the maximum currently used:

Total multi-location fields.
Under Multi-Location Memory, look at Total Fields Used.
Total write locations in multi-location fields.
Under Multi-Location Memory, look at Total Locations Used.
Write locations for this field.
Look at the Write Locations list heading.

To complete changes to the write location list:

Click OK.
If you changed the first write location in the list, you will be prompted to confirm that you want to change the Data to Display area of the field pane's Data tab. This is necessary because it is neither possible nor desirable to have the value displayed for a field not correlate to the value that is edited. Click Yes to accept your write-location-list edits and change the Data to Display area to match the first write location. Click No to return to the Edit Write Locations dialog box.