split screen on VT220

[Ssi]

 I'm trying to get a simple split screen utility working on a VT220
running in VT100 mode. I've created a termcap entry for the
top half and bottom half of the screen to set scroll region,
number of lines etc.
 I have an alias to envoke the termcap entry and move the cursor.
The problem is that `vi' clears to bottom of screen when it
has to scroll the top `window' up, and in the bottom `window'
when I try to cursor up past line one of the file the cursor
jumps to the top of screen, not to line 13 where the origin mode
(DECOM) is set??
 How do I convince `vi' that my terminal only has 12 lines?
For now all I want is for the window not in use to remain
intact while work goes on in the active window.
 The next step is side-by-side windows.
Anyone have any ideas on multiple shells running in separate
areas of the screen ?

                   Greg Ripp (813)628-6100 x5123
                   ...!uunet!pdn!usfvax2!system1!greg