Texas Instruments TI-83 Manual Book page 252

Some screens are never displayed as split screens. For example, if you
press z in
or mode, the mode screen is displayed as a full
Horiz G.T
screen. If you then press a key that displays either half of a split screen,
such as r, the split screen returns.
When you press a key or key combination in either or mode,
Horiz G.T
the cursor is placed in the half of the display for which that key applies.
For example, if you press r, the cursor is placed in the half in which
the graph is displayed. If you press y 0, the cursor is placed in the
half in which the table is displayed.
The TI-83 Plus will remain in split-screen mode until you change back to
screen mode.
Full
TI-83 Plus Split Screen 249