Company | Sunsoft |
Games | 9 in NesCartDB |
Complexity | ASIC |
Boards | JLROM, JSROM, NES-BTR, others |
Pinout | Sunsoft 5 pinout |
PRG ROM capacity | 512K (FME-7) 256K (5A/5B) |
PRG ROM window | 8K×4 + 8K fixed |
PRG RAM capacity | 512K (FME-7) |
PRG RAM window | 8K |
CHR capacity | 256K |
CHR window | 1Kx8 |
Nametable mirroring | H, V, or 1, switchable |
Bus conflicts | No |
IRQ | CPU cycle counter |
Audio | 5B only |
iNES mappers | 069 |
The Sunsoft FME-7 is a mapper IC used by Sunsoft in several of its games. It is nearly identical to the Sunsoft 5A and Sunsoft 5B mapper chips used only in Famicom games, with the 5B notably having expansion audio (see Sunsoft 5B audio).
The FME-7, 5A and 5B are grouped together as iNES Mapper 69.
Both the Sunsoft 5B and FME-7 exist as a 44 pin TQFP chip: diagram
In Europe, boards using the FME-7 were labeled as JSROM and JLROM. The FME-7 mapper was used in only one game released in the US, Batman: Return of the Joker. Many Japanese releases by Sunsoft used the FME-7: Gimmick!, Hebereke, Gremlins 2 (but not in the US version), Barcode World, and others.
Configuration of the FME-7 is accomplished by first writing the command number to the Command Register at $8000-9FFF, then writing the command's parameter byte to the Parameter Register at $A000-BFFF.
There are 16 commands:
On the 5B variant, there are two additional registers at $C000-DFFF and $E000-FFFF that control the audio expansion. See: Sunsoft 5B audio
7 bit 0 ---- ---- .... CCCC |||| ++++- The command number to invoke when writing to the Parameter Register
7 bit 0 ---- ---- PPPP PPPP |||| |||| ++++-++++- The parameter to use for this command. Writing to this register invokes the command in the Command Register.
7 bit 0 ---- ---- BBBB BBBB |||| |||| ++++-++++- The bank number to select for the specified bank.
Bank $0 - PPU $0000-$03FF Bank $1 - PPU $0400-$07FF Bank $2 - PPU $0800-$0BFF Bank $3 - PPU $0C00-$0FFF Bank $4 - PPU $1000-$13FF Bank $5 - PPU $1400-$17FF Bank $6 - PPU $1800-$1BFF Bank $7 - PPU $1C00-$1FFF
7 bit 0 ---- ---- ERbB BBBB |||| |||| ||++-++++- The bank number to select at CPU $6000 - $7FFF |+------- RAM / ROM Select Bit | 0 = PRG ROM | 1 = PRG RAM +-------- RAM Enable Bit (6264 +CE line) 0 = PRG RAM Disabled 1 = PRG RAM Enabled
The FME-7 has up to 6 bits for PRG banking (512 KiB), though this was never used in a game. The 5A and 5B, however, support only 5 (256 KiB)—hence the lowercase 'b' above. The extra address line is instead an audio expansion line, or unused.
It is confirmed that the FME-7 outputs the bank number during accesses to $6000-$7FFF even if RAM is enabled. Though Sunsoft never took advantage of this, it would allow making a cartridge that bank switches up to 256 KiB of PRG RAM. The FME-7 mapper in Loopy's PowerPak mappers, for example, supports 32 KiB.
Open bus occurs if the RAM / ROM Select Bit is 1 (RAM selected), but the RAM Enable Bit is 0 (disabled), i.e. any value in the range $40-$7F. This is a limited form of WRAM write protection on power-up.
NOTE: the enable bit is NOT functional with 2048×8, 32768×8, and 524288×8 RAMs, because those RAMs don't have a +CE input.
There is a tentative report that not all games honor some or any of the bits in this register. Corroboration is needed before any action is taken.
7 bit 0 ---- ---- ..bB BBBB || |||| ++-++++- The bank number to select for the specified bank.
Bank $9 - CPU $8000-$9FFF Bank $A - CPU $A000-$BFFF Bank $B - CPU $C000-$DFFF
The FME-7 has up to 6 bits for PRG banking, but the 5A and 5B support only 5.
These values are the same as MMC1 mirroring modes with the MSB inverted.
7 bit 0 ---- ---- .... ..MM || ++- Mirroring Mode 0 = Vertical 1 = Horizontal 2 = One Screen Mirroring from $2000 ("1ScA") 3 = One Screen Mirroring from $2400 ("1ScB")
7 bit 0 ---- ---- C... ...T | | | +- IRQ Enable | 0 = Do not generate IRQs | 1 = Do generate IRQs +-------- IRQ Counter Enable 0 = Disable Counter Decrement 1 = Enable Counter Decrement
All writes to this register acknowledge an active IRQ.[1] It is not yet known what will happen if this register is written to at the same time as an IRQ would have been generated.
7 bit 0 ---- ---- LLLL LLLL |||| |||| ++++-++++- The low eight bits of the IRQ counter
7 bit 0 ---- ---- HHHH HHHH |||| |||| ++++-++++- The high eight bits of the IRQ counter
Writes to the IRQ counter registers directly set the lower or upper eight bits of the counter. Unlike on MMC3, there is no separate reload latch.
The IRQ feature of FME-7 is a CPU cycle counting IRQ generator. When enabled the 16-bit IRQ counter is decremented once per CPU cycle. When the IRQ counter is decremented from $0000 to $FFFF an IRQ is generated. The IRQ line is held low until it is acknowledged.
Categories: Nintendo licensed mappers, In NesCartDB, Mappers with large PRG RAM, ASIC mappers, Mappers with cycle IRQs, Mappers with single-screen mirroring