UNIF/900218: Difference between revisions
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MAPR '''900218''' describes the PCB used for the pirate port ''Lord of King'' or ''Axe of Fight'' (the pirates evidently hadn't decided), a mapper hack of ''Astynax''. | MAPR '''900218''' describes the PCB used for the pirate port ''Lord of King'' or ''Axe of Fight'' (the pirates evidently hadn't decided), a mapper hack of ''Astynax''. | ||
This has been allocated [[NES 2.0 Mapper 524]]. | |||
It has been modified to use a [[VRC2]], with registers placed compatible with the [[VRC4]]e variant (i.e. registers from $8000-$9004 and $A000-$E00C are thus identical to [[VRC4]]e. ) The register mask is $F00C. | It has been modified to use a [[VRC2]], with registers placed compatible with the [[VRC4]]e variant (i.e. registers from $8000-$9004 and $A000-$E00C are thus identical to [[VRC4]]e. ) The register mask is $F00C. | ||
Latest revision as of 18:06, 30 June 2018
MAPR 900218 describes the PCB used for the pirate port Lord of King or Axe of Fight (the pirates evidently hadn't decided), a mapper hack of Astynax.
This has been allocated NES 2.0 Mapper 524.
It has been modified to use a VRC2, with registers placed compatible with the VRC4e variant (i.e. registers from $8000-$9004 and $A000-$E00C are thus identical to VRC4e. ) The register mask is $F00C.
Additionally, a simple fixed-period IRQ (of 1024 M2 cycles) is mapped to $F008 and $F00C:
- Writes to $F00C (and mirrors) acknowledge an IRQ, reset the timer to 0, and prevent counting
- Writes to $F008 (and mirrors) allow the counter to start
The counter's 1024s bit is inverted into the Famicom's /IRQ line; i.e. if the IRQ is ignored for 1024 cycles it will self-acknowledge.
References
- http://forums.nesdev.org/viewtopic.php?t=12546 lidnariq's forum post (in English)
- http://www.nesbbs.com/bbs/thread-30904-1-1.html zxbdragon's forum post (in Chinese)
- https://github.com/dragon2snow/fceux-dump-project/commit/42233e291693babfb988076dc4934b8708e26eda sloppy patch to FCEUX for support
