Subject: Re: [stella] F4/F6/F8 Bankswitching From: Thomas Jentzsch <tjentzsch@xxxxxx> Date: Sun, 15 Jun 2003 18:49:14 +0200 |
Aaron Bergstrom wrote: > But I'm not clear on how the ASM file is to be structured so that each > bank has an address of $1000 to $1FF3. That's no problem, because due to addressing space limitations of the 6507, e.g. $1000 = $3000 = $5000... You must logical ORG your banks at an odd 4K segment (else you might access the TIA, RAM etc.) E.g. ORG $1000 for the first bank and $3000 for the second bank works good. But some standard is to use the last possible addresses, so you should use $d000 and $f000 for 8K games. Now it get's a bit more complicated: The examples about would create 12K instead of 8K files, because you skip the $2000 or $e000 bank and the assembler will fill that with $FF. But there is RORG. This one is getting important for bankswitched games, because it's only a logical origin and not a also physical one. So your banks could start e.g. like this: ORG $1000 RORG $d000 ... ORG $2000 RORG $f000 Note that you *always* must use ORG and RORG then. Now all you code is assembled for the logical origin, but stored at the physical one and you get a 8K file. Have fun! Thomas _______________________________________________________ Thomas Jentzsch | *** Every bit is sacred ! *** tjentzsch at web dot de | ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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