A86: IY Bit table on the TI-86

To: <assembly-86@lists.ticalc.org>
Subject: A86: IY Bit table on the TI-86
From: "Matthew Johnson" <matt514@gte.net>
Date: Thu, 11 Sep 1997 16:31:53 -0400
Reply-To: assembly-86@lists.ticalc.org

I was looking through Jimmy Mardell's source code of SQRXZ and I noticed he
used such things as these,
(not in this order)

res 1,(iy+$0D) ; _clrLCD, _puts etc doesn't affect the textshadow
set 3,(iy+$05) ; Set flag writing text white on black
res 3,(iy+$05) ; Set it to black on white again

Hmm, I know res and set used to set/reset bits, so I figured they were
changing some kind of bits. But how did this relate to IY? Wasn't IY just
some special 16-bit register? After poking around in the TI-83
documentation, it said that IY is originally
set to the start location of what is a "master bit record" :) Hmm.. the 86
must
be the same. I didn't know that! Then I remembered that Dan told me that,
but that
 was when I didn't even know about IY, or what Dan meant by a bit table,  or
even
 indexed addressing. That was probably over a week and a half ago.

Do you have a list of this bit table Dan? Yeah, I know, it's all
preliminary, untested,
and potentially harmful and/or confidential :-)

I am going to try to compare the Ti83asm.inc
file with the offsets used in the source to see if they are the same.

- Cyber Optic