.SFC File Format – Hardware registers

The register names used in a SNES disassembly

Introduction

A Super Nintendo program controls the picture, the sound and the DMA through registers in the lower half of the system banks ($00–$3F and $80–$BF, offsets below $8000; see the memory map). The explorer’s disassembly puts these names on an operand with the register’s offset, in any bank: the data bank register is not known to a disassembler, and programs set it to zero or to $80 before using them, so the offset alone is what decides. A name is a hint; an lda $2100 in a data bank that is not a system bank reads something else. The names are those the community’s include files use.

Picture processor, $2100–$213F

AddressNameMeaning
$2100INIDISPScreen display: forced blank and brightness
$2101OBSELObject size and base
$2102OAMADDLOAM address, low
$2103OAMADDHOAM address, high and priority
$2104OAMDATAOAM data write
$2105BGMODEBackground mode and tile sizes
$2106MOSAICMosaic size and enable
$2107BG1SCBackground 1 tilemap address and size
$2108BG2SCBackground 2 tilemap address and size
$2109BG3SCBackground 3 tilemap address and size
$210ABG4SCBackground 4 tilemap address and size
$210BBG12NBABackgrounds 1 and 2 character base
$210CBG34NBABackgrounds 3 and 4 character base
$210DBG1HOFSBackground 1 horizontal scroll
$210EBG1VOFSBackground 1 vertical scroll
$210FBG2HOFSBackground 2 horizontal scroll
$2110BG2VOFSBackground 2 vertical scroll
$2111BG3HOFSBackground 3 horizontal scroll
$2112BG3VOFSBackground 3 vertical scroll
$2113BG4HOFSBackground 4 horizontal scroll
$2114BG4VOFSBackground 4 vertical scroll
$2115VMAINVRAM address increment mode
$2116VMADDLVRAM address, low
$2117VMADDHVRAM address, high
$2118VMDATALVRAM data write, low
$2119VMDATAHVRAM data write, high
$211AM7SELMode 7 settings
$211BM7AMode 7 matrix A (and the multiplier operand)
$211CM7BMode 7 matrix B (and the multiplier operand)
$211DM7CMode 7 matrix C
$211EM7DMode 7 matrix D
$211FM7XMode 7 centre X
$2120M7YMode 7 centre Y
$2121CGADDPalette address
$2122CGDATAPalette data write
$2123W12SELWindow mask settings, backgrounds 1 and 2
$2124W34SELWindow mask settings, backgrounds 3 and 4
$2125WOBJSELWindow mask settings, objects and colour window
$2126WH0Window 1 left
$2127WH1Window 1 right
$2128WH2Window 2 left
$2129WH3Window 2 right
$212AWBGLOGWindow mask logic, backgrounds
$212BWOBJLOGWindow mask logic, objects and colour
$212CTMMain screen designation
$212DTSSub screen designation
$212ETMWWindow mask for the main screen
$212FTSWWindow mask for the sub screen
$2130CGWSELColour addition select
$2131CGADSUBColour math designation
$2132COLDATAFixed colour data
$2133SETINIScreen mode and interlace select
$2134MPYLMultiplication result, low (read)
$2135MPYMMultiplication result, middle (read)
$2136MPYHMultiplication result, high (read)
$2137SLHVLatch the horizontal and vertical counters (read)
$2138OAMDATAREADOAM data read
$2139VMDATALREADVRAM data read, low
$213AVMDATAHREADVRAM data read, high
$213BCGDATAREADPalette data read
$213COPHCTHorizontal counter latch
$213DOPVCTVertical counter latch
$213ESTAT77PPU1 status
$213FSTAT78PPU2 status

Sound processor ports and work RAM access

AddressNameMeaning
$2140APUIO0Sound processor port 0
$2141APUIO1Sound processor port 1
$2142APUIO2Sound processor port 2
$2143APUIO3Sound processor port 3
$2180WMDATAWork RAM data
$2181WMADDLWork RAM address, low
$2182WMADDMWork RAM address, middle
$2183WMADDHWork RAM address, high

The ports repeat every four bytes up to $217F; the explorer names only $2140–$2143.

Joypad ports and CPU registers, $4016–$421F

AddressNameMeaning
$4016JOYSER0Joypad serial port 1 (latch and read)
$4017JOYSER1Joypad serial port 2 (read)
$4200NMITIMENInterrupt enable: NMI, timer IRQs and auto joypad read
$4201WRIOProgrammable I/O port (output)
$4202WRMPYAMultiplicand
$4203WRMPYBMultiplier, starts the multiplication
$4204WRDIVLDividend, low
$4205WRDIVHDividend, high
$4206WRDIVBDivisor, starts the division
$4207HTIMELHorizontal timer, low
$4208HTIMEHHorizontal timer, high
$4209VTIMELVertical timer, low
$420AVTIMEHVertical timer, high
$420BMDMAENStart general DMA channels
$420CHDMAENEnable HDMA channels
$420DMEMSELROM access speed
$4210RDNMINMI flag and CPU version
$4211TIMEUPIRQ timer flag
$4212HVBJOYBlanking and auto joypad status
$4213RDIOProgrammable I/O port (input)
$4214RDDIVLQuotient, low
$4215RDDIVHQuotient, high
$4216RDMPYLProduct or remainder, low
$4217RDMPYHProduct or remainder, high
$4218JOY1LJoypad 1 data, low
$4219JOY1HJoypad 1 data, high
$421AJOY2LJoypad 2 data, low
$421BJOY2HJoypad 2 data, high
$421CJOY3LJoypad 3 data, low
$421DJOY3HJoypad 3 data, high
$421EJOY4LJoypad 4 data, low
$421FJOY4HJoypad 4 data, high

DMA channels, $4300–$437F

Channel n (0 to 7) has eleven registers at $43n0 to $43nA. The explorer names them as the wiki does, with the channel number in the name: $4310 is DMAP1, $4372 is A1T7L, $4305 is DAS0L.

AddressNameMeaning
$43n0DMAPnDMA control: direction, mode, step
$43n1BBADnDMA destination register ($21xx)
$43n2A1TnLDMA source address, low
$43n3A1TnHDMA source address, high
$43n4A1BnDMA source bank
$43n5DASnLDMA byte count (or HDMA indirect address), low
$43n6DASnHDMA byte count (or HDMA indirect address), high
$43n7DASBnHDMA indirect bank
$43n8A2AnLHDMA table address, low
$43n9A2AnHHDMA table address, high
$43nANLTRnHDMA reload flag and line counter

Not described

Known, not yet covered

  • Reference: the bits of each register: what each value does is on the sources below, not here.
  • Reference: the register names of the co-processors (SA-1 at $2200, Super FX at $3000, DSP-1, Cx4 and the rest) and the open-bus behaviour of the unused ranges.
  • Viewer: the disassembly does not know the data bank register, so a name on an absolute operand can be wrong when the data bank is not a system bank.

Links

Reference

  • Registers – SNESdev Wiki: the register list with the bits