[A86] Re: The f'n 86 screen
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[A86] Re: The f'n 86 screen
Back when I was writing FD2 I did a lot of playing around with port 3
to get things working optimally. I'm fairly certain bit 1 tells
whether a timer interrupt has occurred, so in Dux's routine there, it
leaves the routine if a timer interrupt has _not_ occurred (ie/ bit 1
is reset). This makes sense since the screen refresh is (sort of)
related to the timer interrupts (ie/ don't mess with the video planes
if it's not on the normal refresh cycle).
IIRC, leaving out that piece of code causes the screen to flicker
slightly when ON is pressed.
The TI85 documentation (ti-ports.txt) states bit 2 is used to check
for timer interrupts, but I'm pretty sure that's wrong.
On Monday, October 01, 2001, Ricky wrote:
> I _think_ you read bit 1 of port 3 to see if the
> screen update is in progress and leave the interuppt
> if it is (if bit 1 is set).
> This code is from Dux Gregis' Blitzgry IM2 4-Level
> Grey-scale routine. This is only a snippit; the full
> code can be found here:
> http://guide.ticalc.org/advanced/gray.htm
> and here.
> http://www.ti-programmers.com/cgi-
> bin/ultimatebb.cgi?ubb=get_topic&f=4&t=000001
> (different explainations)
> ...
> int_start:
> ex af,af' ;its im2
> exx ;
> in a,(3) ;read port 3 (lcd,on key pressed port)
> bit 1,a ;if bit 1 set (equal to 1)
> jr z,leave_int ;leave interuppt
> ...
> Can anyone confirm or deny this?
--
Aaron was here.
acurti1@umbc.edu
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