NES 2.0 Mapper 339

NES 2.0 mapper 339 denotes several very similar MMC3+NROM multicarts, differentiated by submapper numbers that determine the address bits that select NROM-256 over NROM-128 PRG banking mode.

Outer Bank ($6000-$7FFF, write)

A~[0110 .... P.MC Cbba] (Address AND $E000)==$6000, MMC3 $A001.7=1, $A001.6=0
             | || |||+- PRG A14 in NROM-128 mode
             | || |++-- PRG A16..A15 in NROM modes
             | |+-+---- PRG/CHR A18..A17 in all modes
             | +------- 0: NROM-128/-256 PRG mode: PRG A16..A14 from bits "bba", register remains writable
             |          1: MMC3 PRG mode: PRG A16..A14 from MMC3 output, register write-protected
             +--------- 0: Normal PRG-ROM addressing
                        1: PRG A1..A0 from solder pad for menu selection

NROM-256 selection

Every multicart using this mapper has its own method of selecting NROM-256 mode, in which PRG A14 comes directly from CPU A14 rather than the "a" bit, that is denoted by NES 2.0 submapper:

• Submapper 0: NROM-256 if (Address AND $06) == $06 (K-3006 PCB, UNIF MAPR BMC-K-3006)
• Submapper 1: NROM-256 if (Address AND $04) != $00 (unmarked PCB)
• Submapper 2: NROM-256 if (Address AND $11) != $00 (Realtec 8058 PCB)
• Submapper 3: NROM-256 if (Address AND $18) != $00 (K-3091/GN-16 PCB)
• Submapper 4: NROM-256 if (Address AND $14) != $00 (GR-002-31 PCB)

See also

• GR-002-31 PCB analysis