Sunsoft FME-7

From NESdev Wiki
Revision as of 02:27, 2 March 2015 by Rainwarrior (talk | contribs) (→‎Registers: summary of commands)
Jump to navigationJump to search

The Sunsoft FME-7 represents two mapper ICs which work identically, except that one contains extra sound hardware. The FME-7 is the base memory mapper with no additional sound hardware. The Sunsoft 5B is an FME-7 with the addition of extra sound hardware. Both the Sunsoft 5B and FME-7 exist as a 44 pin TQFP. It is emulated as iNES Mapper 069.

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.

Overview

  • Manufacturer: Sunsoft
  • PRG ROM Size: Up to 256 KiB on 5B; Up to 512 KiB on FME-7; at least 256 KiB on 5A but unknown.
  • PRG ROM Bank Size: 8 KiB
  • PRG RAM: Up to 8 KiB, and possibly more
  • CHR capacity: 256 KiB
  • CHR Bank Size: 1 KiB
  • Nametable mirroring: Controlled by Mapper: H, V, 1scA, 1scB
  • Subject to bus conflicts: No

Banks

  • CPU $6000-$7FFF: 8 KB Bankable PRG ROM or PRG RAM
  • CPU $8000-$9FFF: 8 KB Bankable PRG ROM
  • CPU $A000-$BFFF: 8 KB Bankable PRG ROM
  • CPU $C000-$DFFF: 8 KB Bankable PRG ROM
  • CPU $E000-$FFFF: 8 KB PRG ROM, fixed to the last bank of ROM
  • PPU $0000-$03FF: 1 KB Bankable CHR ROM
  • PPU $0400-$07FF: 1 KB Bankable CHR ROM
  • PPU $0800-$0BFF: 1 KB Bankable CHR ROM
  • PPU $0C00-$0FFF: 1 KB Bankable CHR ROM
  • PPU $1000-$13FF: 1 KB Bankable CHR ROM
  • PPU $1400-$17FF: 1 KB Bankable CHR ROM
  • PPU $1800-$1BFF: 1 KB Bankable CHR ROM
  • PPU $1C00-$1FFF: 1 KB Bankable CHR ROM

Registers

Configuration of the FME-7 is accomplished by first writing the command number to the Command Register, then writing the command's parameter byte to the Parameter Register.

There are 16 commands:

  • $0-7 control CHR banking
  • $8-B control PRG banking
  • $C controls nametable mirroring
  • $D-F controls IRQ

Command Register ($8000-$9FFF)

7  bit  0
---- ----
.... CCCC
     ||||
     ++++- The command number to invoke when writing to the Parameter Register

Parameter Register ($A000-$BFFF)

7  bit  0
---- ----
PPPP PPPP
|||| ||||
++++-++++- The parameter to use for this command. Writing to this register invokes the command in the Command Register.

Commands

In order to invoke a command first write the command's number to the Command Register, then the desired parameter to the Parameter Register.

CHR Bank 0 ($0)

7  bit  0
---- ----
BBBB BBBB
|||| ||||
++++-++++- The bank number to select at PPU $0000 - $03FF

CHR Bank 1 ($1)

7  bit  0
---- ----
BBBB BBBB
|||| ||||
++++-++++- The bank number to select at PPU $0400 - $07FF

CHR Bank 2 ($2)

7  bit  0
---- ----
BBBB BBBB
|||| ||||
++++-++++- The bank number to select at PPU $0800 - $0BFF

CHR Bank 3 ($3)

7  bit  0
---- ----
BBBB BBBB
|||| ||||
++++-++++- The bank number to select at PPU $0C00 - $0FFF

CHR Bank 4 ($4)

7  bit  0
---- ----
BBBB BBBB
|||| ||||
++++-++++- The bank number to select at PPU $1000 - $13FF

CHR Bank 5 ($5)

7  bit  0
---- ----
BBBB BBBB
|||| ||||
++++-++++- The bank number to select at PPU $1400 - $17FF

CHR Bank 6 ($6)

7  bit  0
---- ----
BBBB BBBB
|||| ||||
++++-++++- The bank number to select at PPU $1800 - $1BFF

CHR Bank 7 ($7)

7  bit  0
---- ----
BBBB BBBB
|||| ||||
++++-++++- The bank number to select at PPU $1C00 - $1FFF

PRG Bank 0 ($8)

7  bit  0
---- ----
ER.B 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

It is very likely that a cartridge could be modified to support banking up to 256 KiB of PRG-RAM here. However, no game was ever released with more than 8KiB and this is currently untested. At least one version of the FME-7 mapper for the PowerPak supports 32 KiB.

Values $40-$7F produce open bus: the RAM / ROM Select Bit is 1 (RAM selected), but the RAM Enable Bit is 0 (disabled). This is a limited form of WRAM write protection on power-up.

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.

PRG Bank 1 ($9)

7  bit  0
---- ----
...B BBBB
   | ||||
   +-++++- The bank number to select at CPU $8000 - $9FFF

PRG Bank 2 ($A)

7  bit  0
---- ----
...B BBBB
   | ||||
   +-++++- The bank number to select at CPU $A000 - $BFFF

PRG Bank 3 ($B)

7  bit  0
---- ----
...B BBBB
   | ||||
   +-++++- The bank number to select at CPU $C000 - $DFFF

Name Table Mirroring ($C)

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")

IRQ Control ($D)

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.

IRQ Counter Low Byte ($E)

7  bit  0
---- ----
LLLL LLLL
|||| ||||
++++-++++- The low eight bits of the IRQ counter. Note that setting this register directly sets the lower eight bits of the counter.

IRQ Counter High Byte ($F)

7  bit  0
---- ----
HHHH HHHH
|||| ||||
++++-++++- The high eight bits of the IRQ counter. Note that setting this register directly sets the upper eight bits of the counter.

IRQ Operation

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.

How to Use the IRQ Generator

  1. Set the counter to the desired number of cycles minus one.
  2. Enable the IRQ generator by turning on both the IRQ Enable and IRQ Counter Enable flags of the IRQ Control command.
  3. Within the IRQ handler, write to the IRQ Control command to acknowledge the IRQ.
  4. Optional: Go back to Step 1 for the next IRQ.

Disch's Notes

 Here are Disch's (lightly edited) notes:  
 ========================
 =  Mapper 069          =
 ========================
 
 
 aka
 --------------------------
 Sunsoft FME-7
 Sunsoft 5B
 
 
 
 Example Games:
 --------------------------
 Gimmick!
 Batman:  Return of the Joker
 Hebereke
 Gremlins 2 (J)
 
 
 Notes:
 --------------------------
 This mapper is FME-7 and compatible.  Sunsoft 5B operates the same as FME-7, only it has additional sound
 hardware.  For a long time, it was thought Gimmick! uses FME-7, so the expansion sound is labeled as FME-7
 in various places -- however -- technically FME-7 has no extra sound.
 
 Gimmick! is the only known game to use the extra sound found on Sunsoft 5B
 
 
 Registers:
 --------------------------
 
 Range,Mask:   $8000-FFFF, $E000
 
   $8000:  [.... AAAA]   Address for use with $A000
 
   $A000:  [DDDD DDDD]   Data port
     R:0-7 ->  CHR Regs
     R:8-B ->  PRG Regs
     R:C   ->  Mirroring
     R=D-F ->  IRQ Control
 
   $C000:  [.... AAAA]   Address for use with $E000 (sound)
 
   $E000:  [DDDD DDDD]   Data port (sound -- see sound section)
 
 
 PRG Setup:
 ---------------------------
 
 R:8 controls $6000-7FFF.  It can map in PRG-RAM, PRG-ROM, or leave it unmapped (open bus), depending on the
 mode it sets:
 
 R:8:  [ERPP PPPP]
    E = Enable RAM (0=disabled, 1=enabled)
    R = RAM/ROM select (0=ROM, 1=RAM)
    P = PRG page
 
  if E=0 and R=1, RAM is selected, but it's disabled, resulting in open bus.  In case it's still unclear:
 
  R=0:       ROM @ $6000-7FFF
  R=1, E=0:  Open Bus @ $6000-7FFF
  R=1, E=1:  RAM @ $6000-7FFF
 
 
 R:9 - R:B appear to be a full 8 bits:  [PPPP PPPP], and select only ROM.
 
       $6000   $8000   $A000   $C000   $E000  
     +-------+-------+-------+-------+-------+
     |  R:8  |  R:9  |  R:A  |  R:B  | { -1} |
     +-------+-------+-------+-------+-------+
 
 
 No games seem to use more than 8k PRG-RAM, so I'm unsure whether or not it's swappable when selected.  I
 don't see why it wouldn't be.
 
 
 
 CHR Setup:
 ---------------------------
 
       $0000   $0400   $0800   $0C00   $1000   $1400   $1800   $1C00 
     +-------+-------+-------+-------+-------+-------+-------+-------+
     |  R:0  |  R:1  |  R:2  |  R:3  |  R:4  |  R:5  |  R:6  |  R:7  |
     +-------+-------+-------+-------+-------+-------+-------+-------+
 
 
 Mirroring:
 ---------------------------
 
 R:C:  [.... ..MM]
   %00 = Vert
   %01 = Horz
   %10 = 1ScA
   %11 = 1ScB
 
 
 IRQs:
 ---------------------------
 
 This mapper has a 16-bit IRQ counter which decrements every CPU cycle.  When it wraps from $0000->FFFF, an
 IRQ is tripped.
 
  reg R:E sets the low 8 bits of the counter
  reg R:F sets the high 8 bits
 
   Note the regs change the actual counter -- not a reload value.
 
  reg R:D is the IRQ control:
    [C... ...T]
    C = Enable countdown (0=disabled, 1=enabled)
    T = Enable IRQ triggering (0=disabled, 1=enabled)
 
 In order for IRQs to work as expected, both bits must be set.  If either bit is cleared, an IRQ won't occur:
 
  C=0, T=1:  IRQs are enabled, but the counter will never decrement
  C=1, T=0:  Counter decrements, but IRQs are disabled
 
 Acknowledging IRQs can only be done by writing reg R:D
  1. ↑ Test performed in 2015 by Oliveira using IRQ acknowledge test ROM on NESdev BBS
Retrieved from "https://www.nesdev.org/w/index.php?title=Sunsoft_FME-7&oldid=11456"