Table of addresses to render sprites

[codernator]

I am attempting to use indirect addressing to render a sprite, by referencing a table of addresses to various sprite frames. I did read http://atariage.com/forums/topic/198867-address-table-question-urgent/page__hl__+indirect%20+address?do=findComment&comment=2536600, but I seem unable to correctly apply this to my code.

 

What is rendered is not the sprite I intended, but whatever happens to be in whatever address I happen to be incorrectly referencing. Please help me uncover the error.

 

Here is a snippet:

 

FRAME_POINTER will point to the current frame by address. (In this snippet there is only one frame).

 

SEG.U VARS

ORG $80

FRAME_POINTER ds 2

SEG CODE

 

 

LDA TankImageTable

 

STA FRAME_POINTER

LDA TankImageTable + 1

STA FRAME_POINTER + 1

 

Gfx Kernel reducted to only the relevant part.

 

LDY #2

LDX #7

TankArea

LDA (FRAME_POINTER),X

STA GRP0

STY WSYNC

DEX

BPL TankArea

 

Sprite Definition:

 

TankImageFrame0

.byte #%01111110

.byte #%11010101

.byte #%10101011

.byte #%11111110

.byte #%10111000

.byte #%10011000

.byte #%00011000

.byte #%00011000

 

TankImageTable

.word TankImageFrame0

[Omegamatrix]

LDA (FRAME_POINTER),X is not a valid addressing mode. Use LDA (FRAME_POINTER),Y instead. Your compiler shouldn't let it compile. Are you using DASM or something else?

[codernator]

Wow, I feel like such a code monkey. I read the addressing modes over and over, but still didn't pick up what was being laid down.

 

Anyway, it works now.

 

I was using DASM 1.09. I've upgraded to DASM 2.20.11. Either way, no error was reported concerning the invalid addressing mode at any verbosity. :/

[roland p]

I also made this mistake several times with dasm. I wonder Is there any use for indexed indirect addressing mode on the 2600?

[codernator]

Thanks to this post, I now have an animated tank that you can move back and forth on a multi-colored background.

[Thomas Jentzsch]

I wonder Is there any use for indexed indirect addressing mode on the 2600?

Probably there is, but I have never ever used it in more than 10 years of coding.