pceas .BSS directive

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Debvgger
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pceas .BSS directive

Post by Debvgger » Sun Apr 12, 2015 8:23 am

Hi, shouldn't the first bytes declared after the first .BSS directive be allocated into $2000 ? Checking the disassembly in Mednafen's debugger shows the address is $2200.

Are the first 512 bytes reserved for some reason? I'm checking the documentation but I can't find anything about that. Am I breaking something if I put a .ORG $2000 after the first .BSS ?

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MooZ
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Re: pceas .BSS directive

Post by MooZ » Sun Apr 12, 2015 9:57 am

Indeed, .bss starts at $2200.
The first 256 bytes of $2000 is the zero page. You can declare stuffs there using the .zp directive.
Next comes the stack ($2100 - $21ff included). There's no directive. You can still read/write there but you'll most likely shoot yourself in the foot as it's used to store returns addresses, and everything you pushed there with the pha/phx/phy/etc... instructions.

Debvgger
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Joined: Sun Jun 29, 2008 4:30 pm

Re: pceas .BSS directive

Post by Debvgger » Mon Apr 13, 2015 12:53 pm

Ok, understood. I think I'm too used to manage these things by hand :lol:

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