RE: A82: What To Read?
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RE: A82: What To Read?
On Tuesday, July 01, 1997 5:43 PM, Ryan N Gillespie[SMTP:ryan.gillespie@juno.com] wrote:
> I'm interested in making graphics in games and heard something
> about using the display controller directly. Do you know where, on the
> web, I can find information on this, or could you explain it on this
> list? Thanks.
Well... a good resource is the "82-PORTS.TXT" document on Dine Justensen's page (http://www.gbar.dtu.dk/~c958362/ash/index.html). It basically says that port $10 ($ indicates hex) is used to set the current write position on the screen, and the direction that it will increment after a read/write, and port $11 is used to actually read and write from the display. For those who haven't worked with bitmapped displays before, I'll show you how it goes:
Video Data stored on the LCD controller (not directly accessible... you've got to use OUT and IN commands to get to it) is stored so that each each bit represents one pixel on the LCD screen. Bytes are arranged horizontally, so that 12 bytes represent a row, but 63 bytes represent a column.
There's a certain amount of time you must wait between IN's and OUT's to ports $10 and $11, and the built-in TI-82 ROM routines wait much longer than necessary. I've included a function (for ASH) that copies data from anywhere in memory onto the LCD screen *VERY* quickly (I think just about as fast as possible). That way, you can write to a place in memory to set up your screen, then simply call this function when you want what you drew to be zapped on to the screen.
--
Sam Davies <sdavies@mail.trilogy.net>
Showscrn.h
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