INES Mapper 087: Difference between revisions

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{{DEFAULTSORT:087}}[[Category:iNES Mappers]][[Category:CNROM-like mappers]][[Category:in NesCartDB]]
{{DEFAULTSORT:087}}[[Category:iNES Mappers]][[Category:CNROM-like mappers]][[Category:in NesCartDB]]
  Here are Disch's original notes: 
{{Infobox iNES mapper
  ========================
|name=J87
  = Mapper 087          =
|company=Konami, Jaleco, Taito
  ========================
|mapper=87
 
|othermappers=[[iNES Mapper 101|101]]
 
|boards=JF-0x, JF-10 (Jaleco), FC-009 (Taito), MF4034/30xxA (Konami)
  Example Games:
|prgmax=32K
  --------------------------
|prgpage=n/a
  Argus (J)
|chrmax=32K
  City Connection (J)
|chrpage=8K
  Ninja Jajamaru Kun
|busconflicts=No
 
|audio=No
 
}}
  Notes:
{{nesdbbox
  ---------------------------
|ines|87|iNES 087
  Regs are at $6000-7FFF, so these games have no SRAM.
}}
 
 
  Registers:
  --------------------------
 
    $6000-7FFF:  [.... ..LH]
      H = High CHR Bit
      L = Low CHR Bit
 
    This reg selects 8k CHR @ $0000.  Note the reversed bit orders.  Most games using this mapper only have 16k
  CHR, so the 'H' bit is usually unused.


[[iNES Mapper 101]] is the exact same board, but the bits misinterpreted as in order. [[CNROM]] (which postdates mapper 87) is the same but with the bits in order and bus conflicts.
'''J87''' (Also known as Mapper 87) refers to the first "mapper" created for the Famicom. Despite this, no games with this mapper ever made it overseas to USA NES owners. [[iNES Mapper 101]] is the same board, but for a dump that naïvely reversed the CHR bit-order. [[CNROM]] is a later cost-reduced version of this mapper, by cutting down on one logic chip, at the cost of having bus conflicts, and also has the CHR bank order reversed as well.
 
The name "J87" was given to this mapper due to its historical significance, and creation by Jaleco. Otherwise, no "canonical" name was given to this mapper. Jaleco would later upgrade this mapper to become [[iNES Mapper 140]].
 
== Banks ==
* CPU $8000-$FFFF: 16 KB PRG ROM, fixed (if 16 KB PRG ROM used, then this is the same as $C000-$FFFF)
* CPU $C000-$FFFF: 16 KB PRG ROM, fixed
* PPU $0000-$1FFF: 8 KB switchable CHR ROM bank
 
== Registers ==
=== Bank Select ($6000-$7FFF) ===
This will select an 8 KB CHR ROM bank for PPU $0000-$1FFF.
 
7  bit  0
---- ----
xxxx xxLH
        ||
        |+- High CHR bit
        +-- Low CHR bit
 
Some games with this configuration do not use the high CHR bit, as they contain 16 KB of CHR.

Revision as of 06:55, 19 October 2023

J87
Company Konami, Jaleco, Taito
Boards JF-0x, JF-10 (Jaleco), FC-009 (Taito), MF4034/30xxA (Konami)
PRG ROM capacity 32K
PRG ROM window n/a
PRG RAM capacity None
CHR capacity 32K
CHR window 8K
Nametable mirroring Fixed H or V, controlled by solder pads
Bus conflicts No
IRQ No
Audio No
iNES mappers 087, 101
NESCartDB
iNES 087


J87 (Also known as Mapper 87) refers to the first "mapper" created for the Famicom. Despite this, no games with this mapper ever made it overseas to USA NES owners. iNES Mapper 101 is the same board, but for a dump that naïvely reversed the CHR bit-order. CNROM is a later cost-reduced version of this mapper, by cutting down on one logic chip, at the cost of having bus conflicts, and also has the CHR bank order reversed as well.

The name "J87" was given to this mapper due to its historical significance, and creation by Jaleco. Otherwise, no "canonical" name was given to this mapper. Jaleco would later upgrade this mapper to become iNES Mapper 140.

Banks

  • CPU $8000-$FFFF: 16 KB PRG ROM, fixed (if 16 KB PRG ROM used, then this is the same as $C000-$FFFF)
  • CPU $C000-$FFFF: 16 KB PRG ROM, fixed
  • PPU $0000-$1FFF: 8 KB switchable CHR ROM bank

Registers

Bank Select ($6000-$7FFF)

This will select an 8 KB CHR ROM bank for PPU $0000-$1FFF. 

7  bit  0
---- ----
xxxx xxLH
       ||
       |+- High CHR bit
       +-- Low CHR bit

Some games with this configuration do not use the high CHR bit, as they contain 16 KB of CHR.

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