NROM: Difference between revisions
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[[Category:Discrete logic mappers]][[Category:in NesCartDB]] | [[Category:Discrete logic mappers]] [[Category:in NesCartDB]] [[Category:Nintendo licensed mappers]] | ||
The generic designation '''NROM''' refers to the Nintendo cartridge boards NES-NROM-128, NES-NROM-256, their [[Famicom|HVC]] counterparts, and clone boards. The [[iNES]] format assigns [[ | {{Infobox iNES mapper | ||
|name=NROM | |||
|company=Nintendo, others | |||
|mapper=0 | |||
|boards=NROM, HROM*, RROM, RTROM, SROM, STROM | |||
|prgmax=16K or 32K | |||
|prgpage=n/a | |||
|wrammax=2K or 4K in Family Basic only | |||
|wrampage=n/a | |||
|chrmax=8K | |||
|chrpage=n/a | |||
|mirroring=Fixed H or V, controlled by solder pads (*V only) | |||
|busconflicts=Yes | |||
}} | |||
{{nesdbbox | |||
|ines|0|iNES 000 | |||
|unif_wild|-NROM|NROM | |||
|unif_wild|-HROM|HROM | |||
|unif_wild|-RROM|RROM | |||
|unif_wild|-RTROM|RTROM | |||
|unif_wild|-SROM|SROM | |||
|unif_wild|-STROM|STROM | |||
}} | |||
The generic designation '''NROM''' refers to the Nintendo cartridge boards NES-NROM-128, NES-NROM-256, their [[Famicom|HVC]] counterparts, and clone boards. The [[iNES]] format assigns '''mapper 0''' to NROM. | |||
The suffixes 128 and 256 refer to kilobits by Nintendo's own designation; not kilobytes (as is the case with [[UNROM 512]], for example). | |||
== Overview == | == Overview == | ||
* PRG [[ROM]] size: 16 KiB for NROM-128, 32 KiB for NROM-256 (DIP-28 standard [[mask ROM pinout|pinout]]) | * PRG [[ROM]] size: 16 KiB for NROM-128, 32 KiB for NROM-256 (DIP-28 standard [[mask ROM pinout|pinout]]) | ||
* PRG ROM bank size: Not bankswitched | * PRG ROM bank size: Not bankswitched | ||
* PRG RAM: | * PRG RAM: 2 or 4 KiB, not bankswitched, only in Family Basic (but most emulators provide 8) | ||
* CHR capacity: 8 | * CHR capacity: 8 KiB ROM (DIP-28 standard pinout) but most emulators support RAM | ||
* CHR bank size: Not bankswitched, | * CHR bank size: Not bankswitched, see [[CNROM]] | ||
* Nametable [[mirroring]]: Solder pads select vertical or horizontal mirroring | * Nametable [[mirroring]]: Solder pads select vertical or horizontal mirroring | ||
* Subject to [[bus conflict]]s: Yes | * Subject to [[bus conflict]]s: Yes, but irrelevant | ||
== Banks == | == Banks == | ||
All Banks are fixed, | All Banks are fixed, | ||
* CPU $6000-$7FFF: Family Basic only: PRG RAM, mirrored as necessary to fill entire 8 KiB window, write protectable with an external switch | |||
* CPU $8000-$BFFF: First 16 KB of ROM. | * CPU $8000-$BFFF: First 16 KB of ROM. | ||
* CPU $C000-$FFFF: Last 16 KB of ROM (NROM-256) or mirror of $8000-$BFFF (NROM-128). | * CPU $C000-$FFFF: Last 16 KB of ROM (NROM-256) or mirror of $8000-$BFFF (NROM-128). | ||
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== Registers == | == Registers == | ||
None. This has normally no mapping capability whatsoever! | None. This has normally no mapping capability whatsoever! | ||
Nevertheless, tile animation can be done by swapping between pattern tables $0000 and $1000, using [[PPUCTRL]] bits 4-3 as a "poor man's [[CNROM]]". | |||
== Variants == | == Variants == | ||
[[Mask ROM pinout#Variants|RROM and SROM]] are NROM with different CHR ROM pinouts | [[Mask ROM pinout#Variants|RROM and SROM]] are NROM with different CHR ROM pinouts. RTROM and STROM split PRG into two 8KiB ROMs. | ||
HROM is an early NROM variant without the solder pads to select mirroring, only vertical mirroring available (as if the 'H' pad were selected). | HROM is an early NROM variant without the solder pads to select mirroring, only vertical mirroring available (as if the 'H' pad were selected). | ||
Family Basic, released by Nintendo, Sharp, and Hudson, contains 2 KiB WRAM (or 4 KiB WRAM for v3) accessible at $6000-$7FFF and [[PRG RAM circuit|decoded with a 74HC20]], that is backed with 2 AA batteries. The cartridge is equipped with a back up switch that, when enabled, disables all access to WRAM in order to prevent possible data corruption when the Famicom is turned on or off. | |||
[https://nescartdb.com/profile/view/1808/galaxian Galaxian] uses a smaller 8KiB PRG ROM chip. iNES images are all therefore overdumps. | |||
Modern homebrew programs sometimes use mapper 0 with 8 KB of CHR RAM, which would not be supported on official NROM PCBs without rewiring. In theory, [[BNROM]] might be a more appropriate choice. But most emulators will do the right thing with a 16K or 32K PRG ROM with mapper 0. | |||
[[NROM-368]] is a recent invention that allows addressing more memory without bank switching. | |||
== See also == | == See also == | ||
*[[Programming NROM]] | *[[Programming NROM]] | ||
Latest revision as of 12:51, 4 July 2024
NROM
| Company | Nintendo, others |
| Boards | NROM, HROM*, RROM, RTROM, SROM, STROM |
| PRG ROM capacity | 16K or 32K |
| PRG ROM window | n/a |
| PRG RAM capacity | 2K or 4K in Family Basic only |
| PRG RAM window | n/a |
| CHR capacity | 8K |
| CHR window | n/a |
| Nametable mirroring | Fixed H or V, controlled by solder pads (*V only) |
| Bus conflicts | Yes |
| IRQ | No |
| Audio | No |
| iNES mappers | 000 |
The generic designation NROM refers to the Nintendo cartridge boards NES-NROM-128, NES-NROM-256, their HVC counterparts, and clone boards. The iNES format assigns mapper 0 to NROM.
The suffixes 128 and 256 refer to kilobits by Nintendo's own designation; not kilobytes (as is the case with UNROM 512, for example).
Overview
- PRG ROM size: 16 KiB for NROM-128, 32 KiB for NROM-256 (DIP-28 standard pinout)
- PRG ROM bank size: Not bankswitched
- PRG RAM: 2 or 4 KiB, not bankswitched, only in Family Basic (but most emulators provide 8)
- CHR capacity: 8 KiB ROM (DIP-28 standard pinout) but most emulators support RAM
- CHR bank size: Not bankswitched, see CNROM
- Nametable mirroring: Solder pads select vertical or horizontal mirroring
- Subject to bus conflicts: Yes, but irrelevant
Banks
All Banks are fixed,
- CPU $6000-$7FFF: Family Basic only: PRG RAM, mirrored as necessary to fill entire 8 KiB window, write protectable with an external switch
- CPU $8000-$BFFF: First 16 KB of ROM.
- CPU $C000-$FFFF: Last 16 KB of ROM (NROM-256) or mirror of $8000-$BFFF (NROM-128).
Solder pad config
- Horizontal mirroring : 'H' disconnected, 'V' connected.
- Vertical mirroring : 'H' connected, 'V' disconnected.
Registers
None. This has normally no mapping capability whatsoever! Nevertheless, tile animation can be done by swapping between pattern tables $0000 and $1000, using PPUCTRL bits 4-3 as a "poor man's CNROM".
Variants
RROM and SROM are NROM with different CHR ROM pinouts. RTROM and STROM split PRG into two 8KiB ROMs. HROM is an early NROM variant without the solder pads to select mirroring, only vertical mirroring available (as if the 'H' pad were selected).
Family Basic, released by Nintendo, Sharp, and Hudson, contains 2 KiB WRAM (or 4 KiB WRAM for v3) accessible at $6000-$7FFF and decoded with a 74HC20, that is backed with 2 AA batteries. The cartridge is equipped with a back up switch that, when enabled, disables all access to WRAM in order to prevent possible data corruption when the Famicom is turned on or off.
Galaxian uses a smaller 8KiB PRG ROM chip. iNES images are all therefore overdumps.
Modern homebrew programs sometimes use mapper 0 with 8 KB of CHR RAM, which would not be supported on official NROM PCBs without rewiring. In theory, BNROM might be a more appropriate choice. But most emulators will do the right thing with a 16K or 32K PRG ROM with mapper 0.
NROM-368 is a recent invention that allows addressing more memory without bank switching.
