I have a question about what behavior real MMC1 mapper hardware (iNES mapper 001) has when PRG-ROM is written with bit 7 set to reset the 5bit shift register in this mapper. According to "Disch's original notes" at http://wiki.nesdev.com/w/index.php/INES_Mapper_001, when doing a reset "bits 2,3 of reg $8000 are set (16k PRG mode, $8000 swappable)". This is indeed the behavior I observe in FCEUX 2.2.2.
However, the other two documents I could find about the MMC1 mapper make no mention of this behavior where the shift register reset also resets part of the $8000 control register:
http://wiki.nesdev.com/w/index.php/MMC1
http://nocash.emubase.de/everynes.htm#mapper1mmc1prg32k16kvrom8k4knt
Testing with the Nintendulator emulator, I observe the latter behavior where a reset doesn't affect $8000 or do any bank switching on its own.
Does anyone have more information about this particular behavior? Or maybe someone with real hardware could verify which of these two behaviors is correct? Thanks.
However, the other two documents I could find about the MMC1 mapper make no mention of this behavior where the shift register reset also resets part of the $8000 control register:
http://wiki.nesdev.com/w/index.php/MMC1
http://nocash.emubase.de/everynes.htm#mapper1mmc1prg32k16kvrom8k4knt
Testing with the Nintendulator emulator, I observe the latter behavior where a reset doesn't affect $8000 or do any bank switching on its own.
Does anyone have more information about this particular behavior? Or maybe someone with real hardware could verify which of these two behaviors is correct? Thanks.