Help on playfield tables?

[hendersonn]

Hello, I've been poking around with some code, looking at different tutorials and such. I was wondering if I could have someone look at my code concerning the tables where an image might be stored. While it does display the image, when I tweek it, it dosen't really change as I'd expect it to, causing me to believe it's just serendipity (and obviously that's not what I want). I've looked though the forums, but I feel like i'm over thinking something here.

 

Much appreciated,

Matt

aa.asm

aa.bin

[Nukey Shay]

Exactly what is it you are expecting?

[+SpiceWare]

You might like to read my Collect blog entries. It's the step-by-step development of a 2K game.

[+Random Terrain]

You might like to read my Collect blog entries. It's the step-by-step development of a 2K game.

 

For those who don't know, adapted versions of the Collect blog entries and more can be found here:

 

randomterrain.com/atari-2600-memories.html#assembly_language

[hendersonn]

Exactly what is it you are expecting?

Oops, I meant to upload a slightly different file, no matter. In the 'Kernel' loop where it calls the tables, if I replace the broad scope of 'Matt' with specific letters (M__, A__, etc), there is a disconnect somewhere (timing?) and only produces 'M' and the first 'T' followed by a bar trailing below, leaving out the 'A' and the second 'T'.

 

 

You might like to read my Collect blog entries. It's the step-by-step development of a 2K game.

I had been following along for a bit, but wanted to get the basics down before things like logic shifts and whatnot. I'll have to take another look, maybe I missed something.

[hendersonn]

(I don't see an edit button)

 

Spice,

So I went over your Step 3 example and noticed all the graphics were loaded into one large area (DigitGfx). I guess what I'm hung up on is, suppose you wanted to display a 7, followed by an A, then a 3... is it all a matter of turning it on/off at the right time, or is there another way?

[+SpiceWare]

Took a look at your code, didn't have time earlier and assumed you were spelling MATT across the screen, not down it. As such, I thought your timing of the updates to PF0, PF1 and PF2 were off.

 

 

If what you did was change this:

Aaa	sta WSYNC
	lda Matt,x
	sta PF1
	inx
	iny
	sty COLUPF
	cpx #12 ;-------- 6+6=12
	bne Aaa
	bne Kernel

to this:

Aaa	sta WSYNC
	lda A__,x
	sta PF1
	inx
	iny
	sty COLUPF
	cpx #12 ;-------- 6+6=12
	bne Aaa
	bne Kernel

Then the problem is a misunderstanding of the lda aaaa,x command. aaaa refers to an address in memory, denoted in your code by either Matt or A__. The data starting at Matt is the M graphic data. The data starting at A__ is the A graphic data.

 

When determining which data gets loaded into A, the value of X is added to the address. When your program gets to Aaa X has the value of 6. Matt+6 points to the start of the A graphic data, but A__+6 points to the start of the first T graphic data.

 

If you change that code to this:

	ldx #0
Aaa	sta WSYNC
	lda A__,x
	sta PF1
	inx
	iny
	sty COLUPF
	cpx #6 ;-------- 6+6=12
	bne Aaa

you'll get what you're expecting.

 

The edit button goes away after an hour.

 

aa.asm

Edited September 11, 2014 by SpiceWare

[hendersonn]

Thanks, Spice, It's making a lot more sense now.

Much appreciated!