[A86] Re: The f'n 86 screen

To: <assembly-86@lists.ticalc.org>
Subject: [A86] Re: The f'n 86 screen
From: "David Phillips" <david@acz.org>
Date: Mon, 1 Oct 2001 16:05:23 -0700
References: <20011001.153142.716.1.rabidcow@juno.com>
Reply-To: assembly-86@lists.ticalc.org


> I have to wonder when those bits would get cleared...  maybe when writing
> to the port?

I'd imagine so.  You always write a value back out before leaving, even if
you're not switching grayscale pages.

> > bit 1,a     ;if bit 1 set (equal to 1)
> > jr z,leave_int ;leave interuppt
>
> Ok, I may just be confused, but this comment seems wrong.
> Doesn't the "bit" instruction set the zero flag if the bit is zero?
> If so, that would jump if the bit was *clear*...

Yes, that does seem wrong, but that's how all my code is, and I know for a
fact that it works on the real hardware.  I don't have any documents for the
86 that show what bit 1 does.  ti-ports.txt for the 85 shows that bit 1 is
for whether the LCD is on or off.  Did this change on the 86?  It shows bit
2 as being for the timer interrupts.  Maybe it's not the on or off status,
but the LCD refresh status?  Or perhaps it's like the on bit, and is
reversed.  LCD is on/off could be talking about it refreshing, and not
actually being on or off.

References:

[A86] Re: The f'n 86 screen

From: rabidcow@juno.com