[A83] Re: LCD update freq and working with 16bit numbers on the Z80

To: <assembly-83@lists.ticalc.org>
Subject: [A83] Re: LCD update freq and working with 16bit numbers on the Z80
From: "Henk Poley" <HPoley@DDS.nl>
Date: Tue, 11 Sep 2001 16:51:17 +0200
Reply-To: assembly-83@lists.ticalc.org


> Van: Andreas Gustafsson <and_gu@hotmail.com>
>
> >Don't know the timings of _GRBUFCPY_V, but I do know that with
> >ionFastCopy (much faster) I had a framerate of about 144 (while plotting
> >new sprites in between).
> 
> Wow, that is great! With that fastcopy routine I got what appear as at
> least double the framerate of GRBUFCPY! Guess I need to start
> implementing some delays here and there to get things down to
> reasonable speed again.. :)
> One thing I noticed is that at first I had some strange graphics bugs,
> graphics flickering at places it shouldn't be, but when I uncommented
> the 'di' line (I'm guessing Disable Interrupts?) it worked fine. Is it
> common practice to disable interrupts in your program, or is there a
> reason that I would want to have it enabled?

That's strange, do you run a special IM2 interrupt, that outputs to or
reads from the display? (I don't think so, just checking)

I don't have any problems without the DI (as far as I know), although I
haven't tested the 'raw' ionFastCopy in while (I always use the Venus ~FCPY
lib :-). Oh, and yes, "DI" does mean Disable Interrupts.

What ROM version do you have? There are differences in the LCD(-driver)
used in the different Ti-83's (they don't have Flash, so the ROM version
corresponds with the hardware version), some are slower, some are faster.

A thing most people don't know I think: when you do a  "LD A,I" or "LD
A,R", the P-flag gives you the state of the interrupts (EI or DI), or
better "it returns the status of the interrupt-enable flip-flop (IFF) in
the P flag". Don't know any uses of it, but hmm, maybe somebody can think
of one (the Z80 processor builders must thought of some purpose for this I
guess).

	Henk Poley <><