Re: Two lines on the screen = one BASIC line

From: Segher Boessenkool <*segher_at_kernel.crashing.org*> Date: Sat, 11 Feb 2017 16:43:51 -0600 Message-ID: <20170211224350.GN21840@gate.crashing.org> · segher_at_kernel.crashing.org

On Sat, Feb 11, 2017 at 09:48:30PM +0000, Steve Gray wrote:
> The screen editor has something called the "line link" table. Whenever a character is printed to the 40th column the line link table is updated. A bit is set that "links" the line to the one below it. This table is updated when the screen is scrolled as well.
> I did some work understanding this for the PET's editor rom. You can find a commented disassembly here:
> https://github.com/sjgray/cbm-edit-rom/blob/master/disassemblies/edit-4-40-n-60Hz-901499-01-linelink%20analysis.txt
> 
> The C64's code is based on this but will be slightly adapted. Hope it helps.

It is almost the same on the C64, but the polarity of the "is this line
linked" bit is the other way around (0 is not linked, 1 is linked).
LNMX is at the same address on C64 (d5).

Segher

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