Namco 163
Namco 175/340
| Company | Namco |
| Complexity | ASIC |
| Boards | 11xF0x, CSxxx |
| PRG ROM capacity | 512K |
| PRG ROM window | 8K |
| PRG RAM capacity | 8K |
| PRG RAM window | 8K |
| CHR capacity | 256KiB |
| CHR window | 1K |
| Nametable mirroring | H, V, D, L, 1 |
| Bus conflicts | No |
| IRQ | Mapper 19 only |
| Audio | Mapper 19 only |
| iNES mappers | 019, 210 |
The Namco 129 and 163 with expansion sound are assigned to iNES Mapper 19, while simpler variants using the Namco 175 and 340 ICs have hard-wired mirroring and are assigned to iNES Mapper 210. All four were packaged in 48-pin TQFPs.
Many older programs incorrectly identify this mapper by the name Namco 106. Some sources use the name Namcot instead of Namco, as some games and PCBs use this variation on the company name.
Example games:
- Digital Devil Story - Megami Tensei 2
- Final Lap
- Rolling Thunder (J)
- Splatter House
- Mappy Kids
Banks
- CPU $6000-$7FFF: 8 KB PRG RAM bank
- CPU $8000-$9FFF: 8 KB switchable PRG ROM bank
- CPU $A000-$BFFF: 8 KB switchable PRG ROM bank
- CPU $C000-$DFFF: 8 KB switchable PRG ROM bank
- CPU $E000-$FFFF: 8 KB PRG ROM bank, fixed to the last bank
- PPU $0000-$03FF: 1 KB switchable CHR bank
- PPU $0400-$07FF: 1 KB switchable CHR bank
- PPU $0800-$0BFF: 1 KB switchable CHR bank
- PPU $0C00-$0FFF: 1 KB switchable CHR bank
- PPU $1000-$13FF: 1 KB switchable CHR bank
- PPU $1400-$17FF: 1 KB switchable CHR bank
- PPU $1800-$1BFF: 1 KB switchable CHR bank
- PPU $1C00-$1FFF: 1 KB switchable CHR bank
- PPU $2000-$23FF: 1 KB switchable CHR bank
- PPU $2400-$27FF: 1 KB switchable CHR bank
- PPU $2800-$2BFF: 1 KB switchable CHR bank
- PPU $2C00-$2FFF: 1 KB switchable CHR bank
Mapper 19 has the unusual ability to select the internal 2 KB nametable RAM as a CHR bank page, allowing it to be used as CHR RAM in combination with the existing CHR ROM.
Registers
The 163 has 19 registers within $4800-$5FFF and $8000-$FFFF, while the the 175 and 340 only have 12. Each register occupies a range of $800 bytes, so $4800-$4FFF all refers to one register, $5000-$57FF all refers to another register, and so on.
Sound Data Port ($4800-$4FFF) r/w (Namco 129,163 only)
See Namco 163 audio.
IRQ Counter (low) ($5000-$57FF) r/w (Namco 129,163 only)
7 bit 0 ---- ---- IIII IIII |||| |||| ++++-++++- Low 8 bits of IRQ counter
IRQ Counter (high) / IRQ Enable ($5800-$5FFF) r/w (Namco 129,163 only)
7 bit 0 ---- ---- EIII IIII |||| |||| |+++-++++- High 7 bits of IRQ counter +--------- IRQ Enable: (0: disabled; 1: enabled)
CHR and NT Select ($8000-$DFFF) w
| Value CPU writes | Behavior |
|---|---|
| $00-$DF | Always selects 1KB page of CHR-ROM |
| $E0-$FF | If enabled by bit in $E800 and using a N163 or N129, use the NES's internal nametables (even values for A, odd values for B) |
| Write to CPU address | 1KB CHR bank affected | Values ≥ $E0 denote NES NTRAM if |
|---|---|---|
| $8000-$87FF | $0000-$03FF | $E800.6 = 0 |
| $8800-$8FFF | $0400-$07FF | $E800.6 = 0 |
| $9000-$97FF | $0800-$0BFF | $E800.6 = 0 |
| $9800-$9FFF | $0C00-$0FFF | $E800.6 = 0 |
| $A000-$A7FF | $1000-$13FF | $E800.7 = 0 |
| $A800-$AFFF | $1400-$17FF | $E800.7 = 0 |
| $B000-$B7FF | $1800-$1BFF | $E800.7 = 0 |
| $B800-$BFFF | $1C00-$1FFF | $E800.7 = 0 |
| $C000-$C7FF | $2000-$23FF | always |
| $C800-$CFFF | $2400-$27FF | always |
| $D000-$D7FF | $2800-$2BFF | always |
| $D800-$DFFF | $2C00-$2FFF | always |
Note: With mapper 210, a.k.a. Namco 175 or 340, the nametable selection registers have no effect, and nametable RAM cannot be used as CHR-RAM.
It is believed, but untested, that a game could add a normal SRAM and use it instead of the nametable RAM; if so, a game would be able to get 4-screen mirroring and many more pages of CHR-RAM.
Mirroring examples: (Mapper 19 only)
| Mode | $C000 | $C800 | $D000 | $D800 |
|---|---|---|---|---|
| Horizontal | $E0 | $E0 | $E1 | $E1 |
| Vertical | $E0 | $E1 | $E0 | $E1 |
| 1-Screen 0 | $E0 | $E0 | $E0 | $E0 |
| 1-Screen 1 | $E1 | $E1 | $E1 | $E1 |
| Diagonal | $E0 | $E1 | $E1 | $E0 |
| L-Shaped | $E0 | $E1 | $E1 | $E1 |
External PRG RAM enable ($C000-$C7FF) w (Namco 175 only)
7 bit 0
---- ----
.... ...E
|
+- 1: Enable PRG RAM
PRG Select 1 ($E000-$E7FF) w
7 bit 0
---- ----
MMPP PPPP
|||| ||||
||++-++++- Select 8KB page of PRG-ROM at $8000
|+-------- Namco 129, 163 only: Disable sound if set
++-------- Namco 340 only: Select mirroring
0: One-screen A
1: Vertical
2: Horizontal
3: One-screen B
PRG Select 2 / CHR-RAM Enable ($E800-$EFFF) w
7 bit 0
---- ----
HLPP PPPP
|||| ||||
||++-++++- Select 8KB page of PRG-ROM at $A000
|+-------- Disable CHR-RAM at $0000-$0FFF (Namco 129, 163 only)
| 0: Pages $E0-$FF use NT RAM as CHR-RAM
| 1: Pages $E0-$FF are the last $20 banks of CHR-ROM
+--------- Disable CHR-RAM at $1000-$1FFF (Namco 129, 163 only)
0: Pages $E0-$FF use NT RAM as CHR-RAM
1: Pages $E0-$FF are the last $20 banks of CHR-ROM
PRG Select 3 ($F000-$F7FF) w
7 bit 0 ---- ---- ..PP PPPP || |||| ++-++++- Select 8KB page of PRG-ROM at $C000
Write Protect for External RAM AND Sound Address Port ($F800-$FFFF) w (Namco 129, 163 only)
7 bit 0 ---- ---- KKKK DCBA |||| |||| |||| |||+- 1: Write-protect 2kB window of external RAM from $6000-$67FF (0: write enable) |||| ||+-- 1: Write-protect 2kB window of external RAM from $6800-$6FFF (0: write enable) |||| |+--- 1: Write-protect 2kB window of external RAM from $7000-$77FF (0: write enable) |||| +---- 1: Write-protect 2kB window of external RAM from $7800-$7FFF (0: write enable) ++++------ Additionally the upper nybble must be equal to b0100 to enable writes
Any value outside of the range $40-$4E will cause all PRG RAM to be read-only.
Also see Namco 163 audio.
IRQ Operation
The IRQ is a 15-bit CPU cycle up-counter. $5000 and $5800 provide direct access to the counter itself (i.e., this isn't a reload value). Games can read and write to these registers in realtime.
The IRQ counter increments on each CPU cycle. Upon reaching $7FFF, an IRQ is fired, and it stops counting. Writing to $5000 or $5800 will acknowledge any pending IRQs.
See also
- Namcot 106 by goroh, fix by ZW4 and nori, english translation by nori.
- Comprehensive NES Mapper Document by \Firebug\, information about mapper's initial state is inaccurate.
All of the below are in Japanese:
