You can use the Arpeggiator MIDI plug-in with the Smart Controls on a software instrument track. When you turn on the Arpeggiator, chords you play on the keyboard are arpeggiated, or played one note at a time rather than simultaneously.
After you turn on the Arpeggiator, the Arpeggiator pop-up menu appears in the menu bar. You can choose an Arpeggiator preset and adjust Arpeggiator settings, including note order, note range, and octave range from the Arpeggiator pop-up menu. You can also open the Arpeggiator MIDI plug-in window to make further changes.
Click the Arpeggiator button 
in the Smart Controls menu bar.
The Arpeggiator pop-up menu appears in the menu bar.
Turning on the Arpeggiator inserts the Arpeggiator plug-in on the channel strip, after which you can use the Arpeggiator button to bypass the Arpeggiator. You can also open the Arpeggiator plug-in from the channel strip.
Choose a preset from the Arpeggiator pop-up menu in the Smart Controls menu bar.
In the Arpeggiator pop-up menu, do any of the following:
Choose Note Order, then choose the direction of arpeggiated notes from the submenu.
Choose Note Range, then choose a note value for arpeggiated notes, based on the tempo of the song.
Choose Octave Range, then choose how many octaves the arpeggio covers.
Choose Open Arpeggiator from the Arpeggiator pop-up menu in the Smart Controls menu bar.
For full details about using the Arpeggiator MIDI plug-in, see the MIDI plug-ins section of the Logic Pro Instruments manual.