INES Mapper 227: Difference between revisions
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NewRisingSun (talk | contribs) (Rewrite for brevity, correct the solder pad operation (the values x8 are the result of the ROM content at particular locations) and as a template for similar mappers.) |
NewRisingSun (talk | contribs) (categories) |
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[[Category:iNES Mappers | {{DEFAULTSORT:227}}[[Category:iNES Mappers]][[Category:Multicart mappers]][[Category:Mappers with CHR RAM]] | ||
'''iNES Mapper 227''' denotes an address-latch-based multicart circuit board mounting 1 MiB of PRG-ROM plus 8 KiB of unbanked CHR-RAM. A variant used by Chinese RPGs from Nanjing, Waixing (PCB code '''FW-01''') and Yancheng adds 8 KiB battery-backed WRAM. | '''iNES Mapper 227''' denotes an address-latch-based multicart circuit board mounting 1 MiB of PRG-ROM plus 8 KiB of unbanked CHR-RAM. A variant used by Chinese RPGs from Nanjing, Waixing (PCB code '''FW-01''') and Yancheng adds 8 KiB battery-backed WRAM. | ||
Revision as of 20:03, 10 November 2021
iNES Mapper 227 denotes an address-latch-based multicart circuit board mounting 1 MiB of PRG-ROM plus 8 KiB of unbanked CHR-RAM. A variant used by Chinese RPGs from Nanjing, Waixing (PCB code FW-01) and Yancheng adds 8 KiB battery-backed WRAM.
Address Latch ($8000-$FFFF, write)
[A~1... .mLQ OQQP PpMS]
||| |||| |||+-0: PRG A14=p
||| |||| ||| 1: PRG A14=CPU A14
||| |||| ||+- 0: Vertical mirroring
||| |||| || 1: Horizontal mirroring
||| |||+-++-- PRG A16..A14 (inner bank)
||+-|++------ PRG A19..A17 (outer bank)
|| +-------- 0: When CPU A14=1: PRG A16..14=LLL
|| 1: When CPU A14=1: PRG A16..14=PPp
|+----------- Value for PRG A16..14 when CPU A14=1 and O=0
+------------ 0: PRG A3..A0=CPU A3..A0
1: PRG A3..A0=Solder pad 3-0
Power-on value: 0
Effective meaning:
Bit 9 Bit 7 Bit 0 Meaning $200s $080s $001s (L) (O) (S) 0 0 0 Switchable inner 16 KiB bank PPp at CPU $8000-$BFFF, fixed inner bank #0 at CPU $C000-$FFFF (UNROM-like with fixed bank 0) 0 0 1 Switchable inner 16 KIB bank PP0 at CPU $8000-$BFFF, fixed inner bank #0 at CPU $C000-$FFFF (UNROM-like with only even banks reachable, pointless) 1 0 0 Switchable inner 16 KiB bank PPp at CPU $8000-$BFFF, fixed inner bank #7 at CPU $C000-$FFFF (UNROM) 1 0 1 Switchable inner 16 KIB bank PP0 at CPU $8000-$BFFF, fixed inner bank #7 at CPU $C000-$FFFF (UNROM with only even banks reachable, pointless) ? 1 0 Switchable 16 KiB inner bank PPp at CPU $8000-$BFFF, mirrored at CPU $C000-$FFFF (NROM-128) ? 1 1 Switchable 32 KiB inner bank PP at CPU $8000-$FFFF (NROM-256)
- On multicart PCBs (no PRG-RAM/battery), CHR-RAM is write-protected when O=1 and write-enabled when O=0, i.e. write-protected in the NROM-128 and NROM-256 modes.
- When the m bit is set, PRG A3-A0 are replaced with the values of four solder pads, which when the menu code reads particular ROM locations effectively selects one of up to sixteen menus with different game counts.
- Because all bits are cleared on reset, both CPU $8000-$BFFF and $C000-$FFFF are set to 16 KiB bank #0 on reset.
Similar mappers
- INES Mapper 242 is a variant with only up to 512 KiB PRG-ROM that moves the m bit to a different bit location. A variant with two PRG-ROM chips exists as well.
- NES 2.0 Mapper 380 is an incompatible variant with similar functionality.
- NES 2.0 Mapper 449 is an incompatible variant that adds 32 KiB CHR-RAM bankswitching functionality.
See also
- Dumping thread: https://forums.nesdev.org/viewtopic.php?f=9&t=15271
