NES 2.0 Mapper 270: Difference between revisions
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[[Category:Multicart mappers]] | {{DEFAULTSORT:270}}[[Category:Multicart mappers]][[Category:NES 2.0 mappers with submappers]][[Category:MMC3-like mappers]][[Category:Mappers with scanline IRQs]] | ||
'''NES 2.0 Mapper 270''' denotes [[NES 2.0 Mapper 256|OneBus]] console multicarts that use the consoles' universal input/output (UIO) register $412C to bankswitch higher-order PRG address lines or several PRG chips, and select CHR-RAM via $4242. | '''NES 2.0 Mapper 270''' denotes [[NES 2.0 Mapper 256|OneBus]] console multicarts that use the consoles' universal input/output (UIO) register $412C to bankswitch higher-order PRG address lines or several PRG chips, and select CHR-RAM via $4242. | ||
| Line 41: | Line 41: | ||
+--- PRG/CHR A24 | +--- PRG/CHR A24 | ||
=Notes= | =Notes= | ||
* Any $412C bit can only be read from if the corresponding bit in register $412B (UIO input/ | * Any $412C bit can only be read from if the corresponding bit in register $412B (UIO input/output selector) is set to "0" (input). | ||
* Any $412C bit can only be written to if the corresponding bit in register $412B (UIO input/ | * Any $412C bit can only be written to if the corresponding bit in register $412B (UIO input/output selector) is set to "1" (output). | ||
Latest revision as of 06:37, 26 May 2020
NES 2.0 Mapper 270 denotes OneBus console multicarts that use the consoles' universal input/output (UIO) register $412C to bankswitch higher-order PRG address lines or several PRG chips, and select CHR-RAM via $4242.
Submapper 0: Combination
Responds to all bank bits of submappers 1-3 at the same time. This is permissible, since the only bit that is used by several submappers has the same function in each of them.
Submapper 1: Game Prince RS-16
Outer PRG Bank ($412C, write)
D~7654 3210
---------
.... ..A.
+-- PRG/CHR A24
Submapper 2: Family Pocket 638-in-1
Outer PRG Bank ($412C, write)
D~7654 3210
---------
.... ..AB
|+- PRG/CHR A25
+-- PRG/CHR A24
Jumper Cartridge Detection ($412C, read)
D~7654 3210
---------
.... B...
+---- 0: Jumper cartridge not inserted
1: Jumper cartridge inserted
CHR-RAM enable ($4242, write)
D~7654 3210
---------
.... ...C
+- 0: Use normal OneBus CHR banking
1: Use 8 KiB of unbanked CHR-RAM
Submapper 3: Bittboy 300-in-1
Outer PRG Bank ($412C, write)
D~7654 3210
---------
.... .A..
+--- PRG/CHR A24
Notes
- Any $412C bit can only be read from if the corresponding bit in register $412B (UIO input/output selector) is set to "0" (input).
- Any $412C bit can only be written to if the corresponding bit in register $412B (UIO input/output selector) is set to "1" (output).
