If you want to use the top eraser of Xencelabs pen in Paint Tool SAI, please follow the detailed instructions below.
For Paint Tool SAI Ver.1:
First, please install the Xencelabs Driver.
Driver download link:
 Open the Xencelabs Driver, then click on the 3-Button Pen or Thin Pen option on the left.
 If you have added Paint Tool SAI to the application row, please select Paint Tool SAI first in the application row.
 Clicked on the top [Eraser] option to set up.
 Scroll to [Keystroke…] and click on it.
 Input 'E' in Keystroke Keys, and define the shortcut name, for example 'Eraser'.
 Click on [OK] to save the settings.
Then open Paint Tool SAI and test the top eraser function, it should work.
For Paint Tool SAI Ver.2:
When using the Xencelabs pen tablet in Paint Tool SAI Ver.2, First, please use the top eraser of Xencelabs pen to manually click to select the eraser tool of Paint Tool SAI Ver.2, then rotate to the tip of the pen, use the pen tip to draw any line on the canvas, and then rotate to the eraser of pen to test whether the top eraser function can be used normally.
Tips: If you use the top eraser of Xencelabs pen to manually select a tool other than the eraser function, you need to manually select the eraser tool again to continue using the top eraser function.