Namco 163: Difference between revisions

Revision as of 20:46, 10 February 2013

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…4 ($8000-$87FF,$8800,$9000,$9800) w

Write to CPU address	1KB CHR bank affected
$8000-$87FF	$0000-$03FF
$8800-$8FFF	$0400-$07FF
$9000-$97FF	$0800-$0BFF
$9800-$9FFF	$0C00-$0FFF

Note: Only on Mapper 19 = Namco 129/163, 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…8 ($A000-$A7FF,$A800,$B000,$B800) w

Write to CPU address	1KB CHR bank affected
$A000-$A7FF	$1000-$13FF
$A800-$AFFF	$1400-$17FF
$B000-$B7FF	$1800-$1BFF
$B800-$BFFF	$1C00-$1FFF

Note: Only on Mapper 19 = Namco 129/163, 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…4 ($C000-$C7FF,$C800,$D000,$D800) w (Namco 129,163 only)

Write to CPU address	1KB nametable affected
$C000-$C7FF	$2000-$23FF
$C800-$CFFF	$2400-$27FF
$D000-$D7FF	$2800-$2BFF
$D800-$DFFF	$2C00-$2FFF

Value CPU writes	Behavior
$00-$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: With mapper 210, a.k.a. Namco 175 or 340, these nametable selection registers have no effect.

External PRG RAM enable ($C000-$C7FF) w (Namco 175 (340?) 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 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)
|||| |+--- 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)
++++------ 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: