INES Mapper 178: Difference between revisions
NewRisingSun (talk | contribs) (On second thought, take the Jncota variant out of mapper 178, since it uses hard-wired mirroring and would require an ugly heuristic otherwise.) |
NewRisingSun (talk | contribs) (Add submapper 1) |
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{{DEFAULTSORT:178}}[[Category:iNES Mappers]][[Category:Mappers using $4020-$5FFF]][[Category:Mappers with large PRG RAM]]'''iNES Mapper 178''' is used by some games from Waixing (on a PCB named '''FS305'''), Nanjing (on a PCB named '''NJ0430'''), Jncota and Henge Dianzi as well as some educational computers from GameStar, a.k.a. Belsonic. The chipset is designed for using 8 KiB of chip-internal unbanked CHR-RAM, but can address external RAM/ROM as well, banked in 8 KiB amounts. Circuit boards described by iNES Mapper 178 connect external RAM as bankable PRG-RAM mapped to CPU $6000-$7FFF. | {{DEFAULTSORT:178}}[[Category:iNES Mappers]][[Category:Mappers using $4020-$5FFF]][[Category:Mappers with large PRG RAM]]'''iNES Mapper 178''' is used by some games from Waixing (on a PCB named '''FS305'''), Nanjing (on a PCB named '''NJ0430'''), Jncota and Henge Dianzi as well as some educational computers from GameStar, a.k.a. Belsonic. The chipset is designed for using 8 KiB of chip-internal unbanked CHR-RAM, but can address external RAM/ROM as well, banked in 8 KiB amounts. Circuit boards described by iNES Mapper 178 connect external RAM as bankable PRG-RAM mapped to CPU $6000-$7FFF. | ||
A company named ''Gameinis'' uses this chipset along with an infrared sensor built right into the cartridge shell. This sensor will generate IRQs upon detecting movement. As some non-sensor mapper 178 games are bothered by IRQs that they are not expecting, '''Submapper 0''' denotes the absence, '''Submapper 1''' the presence of the infrared sensor, used by at least the following cartridges: | |||
* ''Gameinis Boxing+Soccer'' | |||
* ''Gameinis Ping Pong'' | |||
=Banks= | =Banks= | ||
| Line 49: | Line 53: | ||
$6000-$7FFF: [I... ....] (write only) | $6000-$7FFF: [I... ....] (write only) | ||
I = set to activate interrupts by infrared signal | I = set to activate interrupts by infrared signal | ||
The I bit is set at power-on, i.e. without writing to the $6000-$7FFF register, interrupts will be ''enabled''. | |||
=Errata= | =Errata= | ||
* The commonly-available ROM images of | * The commonly-available ROM images of | ||
Latest revision as of 12:39, 5 April 2020
iNES Mapper 178 is used by some games from Waixing (on a PCB named FS305), Nanjing (on a PCB named NJ0430), Jncota and Henge Dianzi as well as some educational computers from GameStar, a.k.a. Belsonic. The chipset is designed for using 8 KiB of chip-internal unbanked CHR-RAM, but can address external RAM/ROM as well, banked in 8 KiB amounts. Circuit boards described by iNES Mapper 178 connect external RAM as bankable PRG-RAM mapped to CPU $6000-$7FFF.
A company named Gameinis uses this chipset along with an infrared sensor built right into the cartridge shell. This sensor will generate IRQs upon detecting movement. As some non-sensor mapper 178 games are bothered by IRQs that they are not expecting, Submapper 0 denotes the absence, Submapper 1 the presence of the infrared sensor, used by at least the following cartridges:
- Gameinis Boxing+Soccer
- Gameinis Ping Pong
Banks
- CPU $6000-$7FFF: 8 KiB switchable PRG-RAM bank
- CPU $8000-$FFFF: 16/32 KiB PRG-ROM bank, switchable
- PPU $0000-$1FFF: 8 KiB unbanked CHR-RAM
- Nametable mirroring: Switchable horizontal/vertical settings
Registers
Mode Register ($4800)
7654 3210
---------
.... .SSM
||+- Nametable mirroring
|| 0: Vertical
|| 1: Horizontal
++-- PRG banking mode
0: NROM-256/BNROM (PRG A14=CPU A14)
1: UNROM (PRG A14..16=111b if CPU A14=1)
2: NROM-128
3: UNROM but with bit 0 of "fixed" bank selectable
(PRG A15..16=11b if CPU A14=1)
Low PRG Bank Register ($4801)
7654 3210
---------
.... .LLL
+++- PRG A16..A14
This can be considered an inner bank register for UNROM mode.
High PRG Bank Register ($4802)
7654 3210 --------- HHHH HHHH ++++-++++- PRG A24?..A17
This can be considered an outer bank register for UNROM mode.
PRG-RAM Bank register ($4803)
7654 3210 --------- BBBB BBBB ++++-++++- PRG-RAM A20?..A13
PRG-RAM is mapped to CPU $6000-$7FFF and is banked in 8 KiB amounts.
Infrared
Some cartridges have an additional infrared sensor. Infrared receiving is working by having two registers:
$5000-$5FFF: [.... ...V] (read only)
V = read current bit from IR sensor
$6000-$7FFF: [I... ....] (write only)
I = set to activate interrupts by infrared signal
The I bit is set at power-on, i.e. without writing to the $6000-$7FFF register, interrupts will be enabled.
Errata
- The commonly-available ROM images of
- 宠物: 小精灵 IV (Chǒngwù: Xiǎo Jīnglíng IV), headerless CRC32 0xB0B13DBD
- Education Computer 32-in-1 (Game Star) [!], headerless CRC32 0xF834F634
- will not work when emulated using the above description. The meaning of registers $4801 and $4802 is swapped, and an emulator must shift the value of $4802 one bit to the left before ORing with $4801. While it cannot be ruled out that these games use an alternative version of the hardware, the more likely explanation is that these are simply bad dumps (notwithstanding GoodNES 3.23b's [!] tag) where the dumper confused the two bank registers.
- Supposedly, the new PRG bank is only committed when $4801 is written. Emulating this supposed behavior however will break Ping Pong, while commiting the PRG bank after any $480x write does not seem to break anything else.
- Most of the educational computers using this mapper require Dendy video timing and will freeze at various points when run with NTSC timing.
- The Waixing FS305 circuit board connects PRG A14 directly to CPU A14, making all PRG banking modes except BNROM unusable. Since it writes the correct banking mode to $4800, it does not require any special treatment.
