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Nightlord
Registered: Jan 2003
Posts: 131 |
safe zero page addresses
can anybody verify me about whether it is safe to use zero page adresses $14 to $60 considering that no basic code will be run
or are there any more addresses in zero page that are safe to use during assembly coding (besides the $fb-$fe)
thanx |
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Stryyker
Registered: Dec 2001
Posts: 465 |
Try the english version - a text version should be available at http://project64.c64.org/ or so. |
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Nightlord
Registered: Jan 2003
Posts: 131 |
oh man thanx a lot... the project 64 site should solve all my problems. i did not know of that site.... thanx everyone... |
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TDJ
Registered: Dec 2001
Posts: 1879 |
WIsh I found a site that would solve all my problems :) |
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Stryyker
Registered: Dec 2001
Posts: 465 |
http://www.ampland.com/ will help solve your troubles TDJ. Just take matters into your own hands. |
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Cruzer
Registered: Dec 2001
Posts: 1048 |
If you don't use any kernal routines and have turned off the kernal irqs, all zeropage addresses except $00 and $01 can be used without problems. But notice that most of the zeropage will be overwritten when you reset the 'puter. |
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Stryyker
Registered: Dec 2001
Posts: 465 |
With some luck you could use $0 or $1 too. I never go it finely tuned but at times could get a sprite to chang appearance using sprite at $0000 |
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Cruzer
Registered: Dec 2001
Posts: 1048 |
I have never experimented much with using $00/01, so I don't really know what the problems are excactly, other than switching randomly between rom/ram/etc., but I suspect changing $00 can halt the CPU or something. It sure would be kewl with a nice full page of "fast memory". Why the f*** didn't CBM put these control registers in $dxxx like the rest?!?
Btw, another problem that usually occurs is if when the music player uses zp-addresses. I usually switch $d018 to $04, so the zeropage shows up on top of the screen, and then play the music to see if any chars are changing. If that's the case you can still use the whole zp, as long as you copy the bytes used by the player somwhere else after calling the player, and then copy them back b4 calling it again. |
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Graham
Account closed
Registered: Dec 2002
Posts: 990 |
@cruzer:
think of it! $0000/$0001 for the processor port is actually one of the better solutions. if you put it at $Dxxx this would mean that you split the C64 memory + lose one bitmap (remember: the processor port cannot be mapped away!). same with the C128 solution where they put the MMU registers at $FF00+ |
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Oswald
Registered: Apr 2002
Posts: 5017 |
ohyeah, in the VIC article or somewhere else, its written down how to write/read mem locations $00/$01, u can read it
by sprite and bitmap collision detection, and you have to make the vic to read from $00/$01 exactly one cycle after the cpu has written sumth there, or sumth similar :) |
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Stryyker
Registered: Dec 2001
Posts: 465 |
If you can't find it there, try http://www.funet.fi/pub/cbm/documents/chipdata/64doc |
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