Pitch over time with Portamento Start set to NOTE. C4 is played first, then C5, so the pitch glides toward C5. Before it gets there, D4 is played. Because the start is set to NOTE, the pitch jumps straight to C5 (the last note played) and glides down to D4 from there.
Compare Portamento Start: PITCH.
Diagram from the XP-80 Owner’s Manual, © 1996 Roland Corporation, reproduced for educational purposes. Credits & disclaimer.