[A83] Re: ROM Page question

To: <assembly-83@lists.ticalc.org>
Subject: [A83] Re: ROM Page question
From: "David Phillips" <david@acz.org>
Date: Mon, 9 Apr 2001 11:36:22 -0600
References: <F100uXZ2y2Fko8C7wyf00002db7@hotmail.com>
Reply-To: assembly-83@lists.ticalc.org


Someone asked this exact question six months ago, to which I replied:

I'm not for certain where this is documented, but setting the ROM
page for area $4000 requires writing to ports 0 and 2.  Bit 4 of port 0
controls bit 3 of the page number, and bits 0-2 of port 2 control bits 0-2
of the page number.  Credit for this info goes to Rusty Wagner (VTI source
code).  Note that port 0 also controls the link port, so I'm guessing that
the proper way to change the page bit is to read the port first and only
change bit 4.

> I've been tring to figure out how to change the rom page on ti-83. There
is
> plenty of documentation on ti-83+ but i can't find any for ti-83.
>
> Here's few things i found out.
> Ti-83 has 16x16kb rom pages which means there's 16 rom pages total.
> To change the rom page you would access port 2 and write to it.
> When you do the rom page changes. Starting at $4000...
>
> But here's the problem. After running few test i have found that port 2
> works exactly the same as ti82. Which means you can only access 8 rom page
> through port 2. (find ti82 docs for more info)
>
> Some body told me that i have to use the link port to access the other rom
> pages but i'm not sure if this is a fact, and i couldn't figure out how.
>
> If anybody has anyinformation please help me

References:

[A83] ROM Page question

From: "AN Pluto" <anpluto@hotmail.com>