INES Mapper 186
iNES Mapper 186 is used for Fukutake Shoten's Japanese edutainment game Study Box. This information is currently identical to FCEUX's source and should NOT be treated as any more authoritative.
Write mask: $FE03 $4200 write: [RR.. ....] - select one of four 8 KiB PRG-RAM banks at $6000 $4201 write: [.... PPPP] - select one of sixteen 16 KiB PRG-ROM banks at $8000 $4202 write: unknown $4203 write: unknown
TCRF claims that there's a printer interface.
Read mask: $FFFF $4200, $4201, $4203 read: returns $00 $4202 read: returns $40 $4204-$43FF read: returns $FF
The readable ports may have something to do with what Санчез describes as an "Audio Tape reader" and "power supply condition". TCRF additionally mentions a touchpad interface.
$4400-$4FFF: 3 KiB PRG-RAM $6000-$7FFF: 8 KiB PRG-RAM bank (one of four) $8000-$BFFF: 16 KiB switchable PRG-ROM bank $C000-$FFFF: 16 KiB fixed PRG-ROM bank (always bank 0)
Having 35 KiB of PRG-RAM seems unlikely, and probable that the 3 KiB slice overlaps with some of the bankable 32 KiB of RAM. Санчез doesn't say anything more specific, unfortunately.