====== BIOS Functions ======

The Loopy's built-in ROM provides code for common operations such as drawing graphics, playing music, and operating the printer.

This page is intended to list and categorize these functions with brief descriptions. Workflows like adding music and graphics to your homebrew game will be their own separate pages.

[[https://docs.google.com/spreadsheets/d/1Y0LgEqUD9ecm6lZwzL1_wo04XM952WdqCpiu2WO141Q/edit?gid=172085780#gid=172085780 | This google sheet]] was adapted as the starting point.

===== Uncategorized =====
<WRAP center round todo 60%>
TODO categorize these
</WRAP>
==== BiosDefaultInterrupt ====
Offset: 0x0604
<code C>void BiosDefaultInterrupt(void)</code>
Default interrupt handler, turns off printer? and halts


==== BiosVdpMode ====
Offset: 0x0668
<code C>void BiosVdpMode(uchar controllerScanMode, uchar videoHeight240)</code>
Sets VDP controller scanning mode and video height

controllerScanMode: bitfield, 1=mouse, 2=gamepad
==== BiosGetSealType ====
Offset: 0x115C
<code C>uint BiosGetSealType(void)</code>
Detect inserted seal cartridge type from sense switches


==== BiosDecompress4bit ====
Offset: 0x437C
<code C>??? BiosDecompress4bit(void* decompressInfo, void* output)</code>
Decompresses 4-bit graphical data, algo unknown


==== BiosInitSoundTransmission ====
Offset: 0x613C
<code C>void BiosInitSoundTransmission(void)</code>
Initializes sound timer and serial port


==== BiosPlayBgm ====
Offset: 0x61A0
<code C>void BiosPlayBgm(void* soundState, uchar unk, ushort trackIndex, void** trackList)</code>
Play a music track from a list


==== BiosPlaySfx ====
Offset: 0x61B8
<code C>void BiosPlaySfx(void* soundState, uchar unk, ushort sfxIndex, void** sfxList)</code>
Play a sound effect from a list


==== BiosUpdateBgm ====
Offset: 0x6238
<code C>void BiosUpdateBgm(void* soundState, uint unk)</code>
Update music playback (call on timer0 interrupt)

Unk param might be maximum data transfer size
==== BiosDma ====
Offset: 0x66D0
<code C>void BiosDma(void* dmaList, int hwChannel)</code>
Trigger a chain of DMA transfers


==== BiosVsyncIfDma ====
Offset: 0x6A0E
<code C>void BiosVsyncIfDma(void* dmaList)</code>
Only vsyncs if the DMA list is valid


==== BiosVsyncDma ====
Offset: 0x6A48
<code C>void BiosVsyncDma(void* dmaList)</code>
Calls BiosVsync and BiosDma(param, 3)


==== BiosVsync ====
Offset: 0x6A5A
<code C>void BiosVsync(void)</code>
Wait for vsync, read controller register to memory


==== BiosSoundChannels ====
Offset: 0x6AC0
<code C>void BiosSoundChannels(uint channelMode)</code>
Sets sound channel configuration

mode 0: 4ch, 1: 3ch + rhythm, 2: 3ch, others: 1ch
==== BiosSoundVolume ====
Offset: 0x6B50
<code C>void BiosSoundVolume(uint vol23, uint vol4)</code>
Sets sound channel volume control

volume for ch2/3 and ch4; 0: -4dB, 1: -2dB, 2: 0dB. ch1 always 0dB.
==== BiosSoundDemo ====
Offset: 0x6B86
<code C>void BiosSoundDemo(void)</code>
Toggles built-in demo music


==== BiosUnknownDecomp? ====
Offset: 0x7D96
<code C>??? BiosUnknownDecomp?(???)</code>
Some kind of decompression function



===== Interrupt Handlers =====
==== BiosAutoUpdateBgm ====
Offset: 0x648C
<code C>void BiosAutoUpdateBgm(void)</code>
Auto call BiosUpdateBgm with pointer at biosAutoSoundState

Use as alternative to creating your own interrupt handler.

===== Math Functions =====
==== BiosColorInverseGray ====
Offset: 0x2D68
<code C>ushort BiosColorInverseGray(ushort color)</code>
Compute 5bit grayscale from inverse of 15bit RGB

Unknown why it's the inverse. Preserves MSB.
==== BiosValueBlendQuarter ====
Offset: 0x2DC6
<code C>uchar BiosValueBlendQuarter(uchar valueA, uchar valueB)</code>
Blend 3/4 of value A with 1/4 of value B (bytes)


==== BiosColorBlendQuarter ====
Offset: 0x2DE0
<code C>ushort BiosColorBlendQuarter(ushort colorA, ushort colorB)</code>
Blend 3/4 of color A with 1/4 of color B


==== BiosMulS16 ====
Offset: 0x2E68
<code C>int BiosMulS16(short a, short b)</code>
Signed 16bit multiply, 32bit result


==== BiosMulU16 ====
Offset: 0x2E72
<code C>uint BiosMulU16(ushort a, ushort b)</code>
Unsigned 16bit multiply, 32bit result


==== BiosDivU16 ====
Offset: 0x2E7C
<code C>ushort BiosDivU16(ushort a, ushort b)</code>
Unsigned 16bit divide, 16bit result


==== BiosDivS16 ====
Offset: 0x2EA6
<code C>short BiosDivS16(short a, short b)</code>
Signed 16bit divide, 16bit result


==== BiosDivS32 ====
Offset: 0x2EDE
<code C>int BiosDivS32(int a, int b)</code>
Signed 32bit divide, 32bit result

===== Graphics =====
==== BiosPlotLines ====
Offset: 0x37A0
<code C>void BiosPlotLines(short data[], uchar colors[], uchar buf[], short bufW, short bufH, bool bufFmt)</code>
Plots a set of colored vertices joined by lines


==== BiosPlotPolygons? ====
Offset: 0x39AC
<code C>??? BiosPlotPolygons?(???)</code>
Plots polygons?


===== Internal Use =====
==== _B_PrintOp1 ====
Offset: 0x06D4
<code C>??? _B_PrintOp1(???)</code>
Print operation


==== _B_PlotPointInBuffer ====
Offset: 0x394E
<code C>??? _B_PlotPointInBuffer(???)</code>
Plots a point following some rules


==== _B_PlotPointSpecial ====
Offset: 0x3C76
<code C>??? _B_PlotPointSpecial(???)</code>
Plots a 4bpp point with some special modes?


==== _B_PlayBgmPointer ====
Offset: 0x61D8
<code C>void _B_PlayBgmPointer(void* soundState, uchar unk, void* track, void** trackList)</code>
Play a music track by pointer


==== _B_PlaySfxPointer ====
Offset: 0x6374
<code C>void _B_PlaySfxPointer(void* soundState, uchar unk, void* sfx)</code>
Play a sound effect by pointer



===== Not yet analyzed =====
  * 0x069C - ? Does something with sensor and printer registers
  * 0x0FD6 - ? Printing function 1
  * 0x101C - ? Printing function 2
  * 0x1064 - ? Printing function 3
  * 0x10AC - ? Moves some data during print
  * 0x10F4 - ? Moves some data during print
  * 0x1140 - ? Moves some data during print
  * 0x1174 - ? Returns 2 if no seal cartridge inserted
  * 0x1198 - ?
  * 0x1248 - ? DMA print data strip to printer driver (internal)
  * 0x128E - ?
  * 0x134C - ? Something to do with SFX, init?
  * 0x13B0 - ? Triggers some unknown IO read
  * 0x1408 - ?
  * 0x1464 - ? Does a bit of math
  * 0x157E - ? Does a bit of math
  * 0x15D4 - ? Small
  * 0x15F2 - ? Small
  * 0x15FE - ? Small
  * 0x162C - ?
  * 0x1652 - ? Small
  * 0x1662 - ? Small
  * 0x1690 - ?
  * 0x17F4 - ?
  * 0x19BC - ?
  * 0x1A0C - ?
  * 0x1B76 - ?
  * 0x1B9C - ?
  * 0x1C04 - ? Small
  * 0x1C2C - ? Runs printer motor to reset position?
  * 0x1CA0 - ?
  * 0x1CF4 - ?
  * 0x1DDE - ? Small
  * 0x1E1C - ?
  * 0x1F5E - ?
  * 0x2038 - ?
  * 0x20EC - ?
  * 0x212E - ?
  * 0x2148 - ?
  * 0x2382 - ?
  * 0x2598 - ?
  * 0x2798 - ?
  * 0x2A24 - ?
  * 0x2AD0 - ?
  * 0x2B0E - ?
  * 0x2B48 - 
  * 0x2F74 - 
  * 0x3088 - 
  * 0x3560 - 
  * 0x35E6 - 
  * 0x36BA - 
  * 0x3736 - 
  * 0x3E64 - 
  * 0x3E9C - 
  * 0x3EF0 - 
  * 0x3F48 - 
  * 0x3FD8 - 
  * 0x40DC - 
  * 0x4186 - 
  * 0x429C - 
  * 0x436A - 
  * 0x445C - 
  * 0x452C - 
  * 0x4640 - 
  * 0x47A4 - 
  * 0x49A4 - 
  * 0x4B20 - 
  * 0x4BA8 - 
  * 0x4C38 - 
  * 0x4CDE - 
  * 0x4D22 - 
  * 0x4E34 - 
  * 0x4FE4 - 
  * 0x5060 - 
  * 0x5098 - 
  * 0x5138 - 
  * 0x51C8 - 
  * 0x542E - 
  * 0x544C - 
  * 0x5474 - 
  * 0x54B8 - 
  * 0x5574 - 
  * 0x55B8 - 
  * 0x55FC -