- For making cartridges of your Super NES games, see Reproduction.
I find myself wondering whether it would be any "better" if you didn't represent 1KiB per tile but instead just 256 bytes, for a 1056x1088 image instead. Probably not...
Where did the name "SFRs" come from? I know them as "MMIO areas". Corrected below.lidnariq wrote:Other than the weirdness where there's two rows for the SFRs in banks $80-$BF but only one in banks $00-$3F, it looks good?
Anyone know what the standard battery RAM addresses are in LoROM and HiROM?
- Corrected size of MMIO areas in banks $80-$BF
- s-cpu_address_space.png (4.94 KiB) Viewed 13809 times
Nocash's fullsnes claims that LoROM puts save RAM in banks $70-$7D and $F0-$FF, either just the lower half (pages $00-$7F) or the entire 64 KiB, and that HiROM puts save RAM in a whole slew of different places, always pages $60-$7F, most often banks $20-$3F and $A0-$BF, but sometimes banks $1x, $3x, $9x, and $Bx; or banks $80-$BF.
There are dozens of board layouts that place cartridge ROM and RAM in different places, and sometimes have certain areas be open bus.lidnariq wrote:Nocash's fullsnes claims that LoROM puts save RAM in banks $70-$7D and $F0-$FF, either just the lower half (pages $00-$7F) or the entire 64 KiB, and that HiROM puts save RAM in a whole slew of different places, always pages $60-$7F, most often banks $20-$3F and $A0-$BF, but sometimes banks $1x, $3x, $9x, and $Bx; or banks $80-$BF.
Categorizing SNES mapping as "LoROM" or "HiROM" is like rounding pi to 3. It'll give you the gist of it, but don't bother trying to use it for anything serious.
You can find specific board layouts here:
http://code.google.com/p/higan/source/b ... Boards.bml
Shouldn't the HiROM map also show ROM (mirror) in bank 40-7Dh? I don't know if/how many games use that area for ROM, but I would have thought that ROM is mapped/mirrored there in most cartridges (of course ROM is usually also mirrored here and there, and it wouldn't be helpful to show all of those mirrors - because they are rather unwanted dirt effects than actually used memory areas).
Maybe it would make sense to add a headline saying "Banks" above of the 00-FF values, and something similar saying "Offset" for 0-FFFF. And something pointing out that 8bit:16bit "Bank:Offset" can be also expressed as 24bit "Address". But if the images are used on wiki/webpage, then that could be explained in the page text, not in the image.
Anyways, it's probably better to keep it simple (or even a bit simplified) without too many details.
The board puts it there, but I don't really think game programmers were meant to use it there. It's not like the $80-$BF mirrors, which are good for having half a bank of ROM in the same data bank as low RAM and I/O, or the mirror at $00, which is good for interrupt stubs that jml to the real handler in fast ROM. It's just another copy of the ROM sitting there in the slow area. Further, if a game gets upgraded to mode $25 ("ExHiROM"), reliance on $40-$7D and $80-$FD carrying the same data would break. So HiROM's mirror in $40-$7D might be considered what you call a "dirt effect".nocash wrote:Shouldn't the HiROM map also show ROM (mirror) in bank 40-7Dh?
MEMSEL ($420D; corresponds to WAITCNT in Game Boy Advance and EXMEMCNT in Nintendo DS)
Write 0 for slow ROM in $80-$FF or 1 for fast ROM in $80-$FF
My init code sets MEMSEL based on the cartridge header:
Code: Select all
MEMSEL = $80420D map_mode = $00FFD5 ; ... lda f:map_mode and #$10 beq not_fastrom inc a not_fastrom: sta MEMSEL
Though I wonder why in the manual they specify the Mode 20 ROM area to be in the SlowROM banks, and the mirrored ROM to be in the upper banks instead of the other way around, if the upper banks can do fast or slow speeds.
if you are in the lower banks it will always be slow and thus it won't fail, in that if MEMSEL gets the wrong value somehow, it will still be slow access and your cart will work.