(Insert stupid Blog name here)

To make use of CDF, you would have to create a new kernel.

 

Not necessarily. Just need to do this before the kernel to point the datastream at a specific location in Display Data RAM, TrackData = $0003:

 lda #<TrackData
 sta DSPTR
 lda #>TrackData
 sta DSPTR

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this periodically during the kernel to save the readings *:

 lda SWCHA ; 3  3
 sta DSWRITE ; 4  7

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This just before processing player's movement:

 ldx #FASTON  ; this overrides LDA #, required for LDA #DSCOMM to get data back from ARM
 stx SETMODE
 ldx #0 ; point datastream at $0000 in Display Data RAM
 stx DSPTR
 stx DSPTR
 ldx #DECODE_TRACKBALL 
 stx DSWRITE ; stored in Display Data $0000
 ldx #$FF
 stx CALLFN ; run ARM routine to decode data stored in TrackData
 lda #DSCOMM ; returns value from Display Data $0001
 sta X_MOVEMENT ; or use it right now, though at this point LDA # is overridden which may complicate things
 lda #DSCOMM ; returns value Display Data $0002
 sta Y_MOVEMENT ; same as above
 ldx #FASTOFF ; restore normal LDA # functionality
 stx SETMODE

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* I'm not familiar with the kernel, if you can't squeeze this in often enough then this idea won't work.

Nevermind - I see Crystal Castles is using a SARA which would conflict with CDF.

 

Maybe a new bankswitch scheme could be done that implements SARA and provides just enough functionality for a single datastream to send data to/get data from the ARM and call ARM funnctions.

@Nathan: I found some minor potential startup issues in the ROMs, especially in SpaceMaster X-7, but also in Centipede and probably in Colony 7 too. The carts may randomly not start correctly to the title screen.

 

Did you experience such problems?

 

I might have seen that once or twice, but I really didn't take notice because of the other problem. Once I had a game running I played it for awhile. I wasn't powering on and off each one.

 

BTW: How do you plan to show the supported controllers on the labels for those games which do not support all controllers in one cart? I suppose that only affects SWTAG and Marble Craze.

Still discussing that with Albert. But it will be some additional text on the end label. TB, AT, AM, something along those lines. Just enough to tell them apart. We'll have a note about it in the instruction card, too.

So it might be possible. But I will definitely leave that to experienced ARM programmers.

If you have time, give them a few tries, please. Space Master should fail about 50%, the others about every 8th time.