INES Mapper 040

iNES Mapper 040 describes yet another pirate port of SMB2j from the FDS to a cartridge. It is very similar to mapper 50.

This description was produced from the source code of FCEUX and Nestopia.

 Registers:
 ---------------------------
 Range,Mask:   $8000-FFFF, $E000

   $8000:  Disable and acknowledge IRQ
   $A000:  Enable IRQ
   $E000:  8 KiB bank mapped at $C000
 
 PRG Setup:
 ---------------------------
 
       $6000   $8000   $A000   $C000   $E000  
     +-------+-------+-------+-------+-------+
     | { 6 } | { 4 } | { 5 } | $E000 | { 7 } |
     +-------+-------+-------+-------+-------+

Like mapper 50, this hardware produces an interrupt 4096 M2 cycles after the IRQ is enabled.

The corresponding hardware is a [url=https://forums.nesdev.org/viewtopic.php?p=217200#p217200]CD4020 functioning as a 13-bit counter[/url], and if the software doesn't acknowledge the interrupt for another 4096 cycles it will self-acknowledge.

See also

• SMB2j aka "The Lost Levels" Mapper #40 Info by The Mad Dumper.