[stella] Now I've got it!!!! Sorry gang!

Subject: [stella] Now I've got it!!!! Sorry gang!
From: crackers@xxxxxxxxxxxxxxxxxxxxxx
Date: Sun, 9 Mar 1997 02:24:13 -0500 (EST)
Okay, I found out why my programme wouldn't draw a picture on a real 2600.
It wasn't completing the Vertical Blank properly because of a typo.

This is the way the verticle blank subroutine should look.

-----------------------------------------------------------------------------
vertb	LDX  #$00         ;thank you Nick Bensema for teaching us all
	LDA  #$02         ;how to do a vertical blank.  
	STA  WSYNC        ;who knows if I could have figured out this one 
	STA  WSYNC        ;on my own. I want to have your baby!
	STA  WSYNC
	STA  VSYNC        ;<- here was one of my 5:00 in the morning errors.
	STA  WSYNC        ;I had typed WSYNC instead of VSYNC. Bleary eyes 
	STA  WSYNC        ;and programming make a deadly combination!
	LDA  #$2C
	STA  TIM64T       ;much like cheese burgers an loneliness. 
	LDA  #$00
	STA  CXCLR        ;<- don't know why I left this in... but what the 
	STA  WSYNC        ;heck it looks cute.
	STA  VSYNC        ;**********CHANGED CODE FROM ORIGINAL**************
	RTS               ;had made another stupid 5am error. (STA WSYNC)
-----------------------------------------------------------------------------

In my original code that last line before the RTS read...

        STA  WSYNC

Be very careful when writing code. That's twice in the same programme
(in the same sub routine) that I've made that typo. And it's not an easy
typo to catch either because it looks like proper code unless you pay
attention.

It also brings up another point. The Atari PC Emulator didn't crash on this
error like a real 2600 did. 

Why?

In anycase, from now on I'm not just going to take the Emulator's word for
it that a programme works. I'll be sure to double check it on a real
Atari 2600. 

Sorry about all the mess. If you're using the code be sure to change the
line to the proper one.

Man... it's something else to see a screen drawn on a real live 2600 and
be able to say "I made it do that!"

I can't wait to see what I can make it do next!

                                    CRACKERS
                          (One happy hacker from hell!!!)


-- 

Accordionist - Wethifl Musician - Atari 2600 Collector | /\/\
http://www.freenet.hamilton.on.ca/~ad329/Profile.html  | \^^/
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