Namco 163

The Namco 106 group are ASIC mappers. 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 simpler mirroring and are assigned to iNES Mapper 210.

Overview

• PRG ROM size: Up to 512 KB
• PRG ROM bank size: 8 KB
• PRG RAM: Up to 8 KB
• CHR capacity: Up to 256 KB ROM and/or 32 KB RAM simultaneously
• CHR bank size: 1 KB
• Nametable mirroring: Controlled by mapper (Mapper 19), hardwired (Mapper 210)
• Subject to bus conflicts: No

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

Registers

The n106 has 19 registers within $4800-$FFFF, except $6000-$7FFF which is WRAM. 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 Select 1 ($8000-$87FF) w

7  bit  0
---- ----
CCCC CCCC
|||| ||||
++++-++++- Select 1KB page of CHR-ROM or CHR-RAM at $0000

Note: Pages $E0-$FF are CHR-RAM, as long as $E800.6 is set to 0. If $E800.6 is set to 1, then pages $E0-$FF refer to the last $20 pages of CHR-ROM as you'd expect.

CHR Select 2 ($8800-$88FF) w

7  bit  0
---- ----
CCCC CCCC
|||| ||||
++++-++++- Select 1KB page of CHR-ROM or CHR-RAM at $0400

Note: Pages $E0-$FF are CHR-RAM, as long as $E800.6 is set to 0. If $E800.6 is set to 1, then pages $E0-$FF refer to the last $20 pages of CHR-ROM as you'd expect.

CHR Select 3 ($9000-$97FF) w

7  bit  0
---- ----
CCCC CCCC
|||| ||||
++++-++++- Select 1KB page of CHR-ROM or CHR-RAM at $0800

Note: Pages $E0-$FF are CHR-RAM, as long as $E800.6 is set to 0. If $E800.6 is set to 1, then pages $E0-$FF refer to the last $20 pages of CHR-ROM as you'd expect.

CHR Select 4 ($9800-$9FFF) w

7  bit  0
---- ----
CCCC CCCC
|||| ||||
++++-++++- Select 1KB page of CHR-ROM or CHR-RAM at $0C00

Note: Pages $E0-$FF are CHR-RAM, as long as $E800.6 is set to 0. If $E800.6 is set to 1, then pages $E0-$FF refer to the last $20 pages of CHR-ROM as you'd expect.

CHR Select 5 ($A000-$A7FF) w

7  bit  0
---- ----
CCCC CCCC
|||| ||||
++++-++++- Select 1KB page of CHR-ROM or CHR-RAM at $1000

Note: Pages $E0-$FF are CHR-RAM, as long as $E800.7 is set to 0. If $E800.7 is set to 1, then pages $E0-$FF refer to the last $20 pages of CHR-ROM as you'd expect.

CHR Select 6 ($A800-$AFFF) w

7  bit  0
---- ----
CCCC CCCC
|||| ||||
++++-++++- Select 1KB page of CHR-ROM or CHR-RAM at $1400

Note: Pages $E0-$FF are CHR-RAM, as long as $E800.7 is set to 0. If $E800.7 is set to 1, then pages $E0-$FF refer to the last $20 pages of CHR-ROM as you'd expect.

CHR Select 7 ($B000-$B7FF) w

7  bit  0
---- ----
CCCC CCCC
|||| ||||
++++-++++- Select 1KB page of CHR-ROM or CHR-RAM at $1800

Note: Pages $E0-$FF are CHR-RAM, as long as $E800.7 is set to 0. If $E800.7 is set to 1, then pages $E0-$FF refer to the last $20 pages of CHR-ROM as you'd expect.

CHR Select 8 ($B800-$BFFF) w

7  bit  0
---- ----
CCCC CCCC
|||| ||||
++++-++++- Select 1KB page of CHR-ROM or CHR-RAM at $1C00

Note: Pages $E0-$FF are CHR-RAM, as long as $E800.7 is set to 0. If $E800.7 is set to 1, then pages $E0-$FF refer to the last $20 pages of CHR-ROM as you'd expect.

Nametable Select 1 ($C000-$C7FF) w (Namco 129,163 only)

7  bit  0
---- ----
NNNN NNNN
|||| ||||
++++-++++- Select nametable at $2000:
             $00-$DF: Use a 1KB page of CHR-ROM as a nametable
             $E0-$FF: Use the NES's internal nametables (even values for A, odd values for B)

Note: On mapper 210, this register has no effect.

External PRG RAM enable ($C000-$C7FF) w (Namco 175 (340?) only)

7  bit  0
---- ----
.... ...E
        |
        +- 1: Enable PRG RAM

Nametable Select 2 ($C800-$CFFF) w (Namco 129,163 only)

7  bit  0
---- ----
NNNN NNNN
|||| ||||
++++-++++- Select nametable at $2400:
             $00-$DF: Use a 1KB page of CHR-ROM as a nametable
             $E0-$FF: Use the NES's internal nametables (even values for A, odd values for B)

Note: On mapper 210, this register has no effect.

Nametable Select 3 ($D000-$D7FF) w (Namco 129,163 only)

7  bit  0
---- ----
NNNN NNNN
|||| ||||
++++-++++- Select nametable at $2800:
             $00-$DF: Use a 1KB page of CHR-ROM as a nametable
             $E0-$FF: Use the NES's internal nametables (even values for A, odd values for B)

Note: On mapper 210, this register has no effect.

Nametable Select 4 ($D800-$DFFF) w (Namco 129,163 only)

7  bit  0
---- ----
NNNN NNNN
|||| ||||
++++-++++- Select nametable at $2C00:
             $00-$DF: Use a 1KB page of CHR-ROM as a nametable
             $E0-$FF: Use the NES's internal nametables (even values for A, odd values for B)

Note: On mapper 210, this register has no effect.

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 are 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 are 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)
|||| ++--- Same for $7000 and $7800 respectively
++++------ Must = b0100 to enable writes

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. However, it is unknown if the counter wraps to $0000 afterwards. Reading/Writing to $5000 or $5800 will acknowledge any pending IRQs.

References

All of the below are in Japanese:

• Naruko's post to the forum
• Wiki on same
• Naruko's blog's post on mirroring on the 340
• Naruko's blog's post on the write protect register at $F800