INES Mapper 241

iNES Mapper 241 denotes a BxROM-like circuit board with the addition of 8 KiB of WRAM at CPU $6000-$7FFF that can be battery-backed. INES Mapper 034 is not commonly used for BNROM with WRAM, because the WRAM's address space is partially overlaid by registers from the NINA-001 part of the mapper specification (although that could be alleviated by disabling the NINA-001 registers in the absence of CHR-ROM).

BxROM with WRAM is typically used natively by games from Henge Dianzi with hard-wired mirroring and a few educational computer cartridges, but is more commonly used as a target for mapper hacks of games that originally used mappers 164, 178 and 227. Because those mapper hacks rarely take bus conflicts into consideration, mapper 241 should be emulated without bus conflicts. As a result of being mapper hacks, such games may also access registers in the $4800-$5FFF range.

Mirroring is hard-wired to horizontal or vertical; INES Mapper 177 denotes a variant with mapper-controlled two-screen mirroring.

LPC Speech Chip

A number of educational computer cartridges, English- as well as Chinese-language, additionally mount a TMS5220C-data-compatible LPC speech chip. The bitstream data is in the TMS5220C-PE LPC format and is sent four bits at a time. Refer to the TMS5220 data sheet, U.S. Patents 4,209,844, 4,331,836 and 4,335,277 as well as MAME's source code for details on the LPC data format and LPC decoding. Note that the hardware interface is different from that of a regular TMS5220.

LPC Chip Status ($5000-5FFF, read)

D~[.R.. ....]
    +--------- 1=Ready to receive data

LPC Data ($5000-5FFF, write)

D~[.R.R DDDD]
    | | ++++-- LPC data
    +-+------- Both set: normal operation
               Both clear: reset chip