INES Mapper 172: Difference between revisions

From NESdev Wiki
Jump to navigationJump to search
mNo edit summary
(Errata, PCB images, Board name)
Line 1: Line 1:
INES Mapper 172 is used by games from ''Super Mega''.
INES Mapper 172 is used to denote the P-4070 board, used the following games:


* ''1991 賭馬 Racing'' (1991 Dǔmǎ Racing, "Enjoyable Horse Racing")
* ''1991 賭馬 Racing'' (1991 Dǔmǎ Racing, "Enjoyable Horse Racing")
Line 26: Line 26:


==Errata==
==Errata==
* The TXC re-release of ''麻将方块 (Mahjong Block)'' uses [[INES Mapper 136]].
* The TXC re-release of ''麻将方块 (Mahjong Block)'' uses [[INES Mapper 132]].


==Similar Mappers==
==Similar Mappers==
The board is identical to [[INES Mapper 136]] except that the CPU bits D0-D5 are connected in reverse order.
The board is identical to [[INES Mapper 136]] except that the CPU bits D0-D5 are connected in reverse order.
==See also==
[http://forums.nesdev.org/viewtopic.php?f=3&t=15961&p=213362#p210703 PCB images]

Revision as of 12:08, 9 February 2018

INES Mapper 172 is used to denote the P-4070 board, used the following games:

  • 1991 賭馬 Racing (1991 Dǔmǎ Racing, "Enjoyable Horse Racing")
  • 麻将方块 (Mahjong Block) (original release)
  • Venice Beach Volley (Super Mega release)

Banks

  • PPU $0000-$1FFF: 8 KB switchable CHR ROM bank

Registers

Mapper 172 uses a custom IC (marked "JV001") serving as a latch, adder and inverter. There are five registers: Input (6 bits), Output (6 bits), Register (6 bits), Mode (1 bit) and Invert (1 bit).

Mask: $E103
Read $4100-$4103: [..RR RRRR]: Read Register. Bits 4-5 are inverted if Invert==1. Bits 6-7 are open bus. Note that the bit order D0-D5 is reversed.
Write $4100: When Mode==0: Bits 0-5 of Register := Input, bits 0-3 being inverted if Invert==1.
             When Mode==1: Bits 0-3 of Register incremented by one, bits 4-5 unaffected.
Write $4101: Invert := Written value bit 5.
Write $4102: Input := Written value bits 0-5. Note that the bit order D0-D5 is reversed.
Write $4103: Mode := Written value bit 5.
Write $8000-$FFFF: Output := Register; written value is ignored.

In Mapper 172, bits 0/1 of the 8 KiB CHR ROM bank number (CHR A13/A14) come from Output 5/4, or 0/1 after taking the reverse bit order into account:

8 KiB CHR-ROM bank number := (Output &3);

Games will check the lower six bits of $4100 for the correct value after several increment and inversion operations as a copy-protection measure.

Errata

Similar Mappers

The board is identical to INES Mapper 136 except that the CPU bits D0-D5 are connected in reverse order.

See also

PCB images