AICA soundsystem of the Dreamcast
by Lars Olsson <jlo@ludd.luth.se>
v0.1 (rough notes), 2001-Jun-15


The AICA registers are mapped both to the SH4 and the ARM7.
The base address is 0x00800000 on the ARM7-side and
0xa0700000 on the SH4-side.

The ARM7 is running at 25MHz (possibly slower...must do some checking)

It appears the registers are really 16-bit but arranged
on 32-bit boundries. The ARM7 can access the registers
either as 32-bit words or as 8-bit; the SH4 can only
access them as 32-bit (because of the G2 FIFO).



00800000 - 00802000: (64 sound channels)

each channel consists of 32 32-bit registers.


00800000 (ch0_cfg_addr_hi)
+----------------------------------------------------------------+
| 31-16 | 15-14     | 13-11 | 10 | 9    | 8-7    | 6-5 | 4-0     |
| n/a   | key-event | n/a   | u  | loop | format | n/a | addr_hi |
+----------------------------------------------------------------+

	key-event:
		00: no change (or key off? need to recheck)
		01: no change
		10: key-off
		11: key-on

		(note: if loop is set it must be cleared for the waveform
		       to stop playing)

	u:
		only noise when set :/
		(could be direction...im only using ADPCM waveform, which
		could explain the noise..if so it rocks!!! (for my
		xm-player that is, no need to waste sample-space by doing
		repeats and stuff for ping-pong loops =)

	loop:
		0: waveform is played once
		1: waveform is repeated according to loop-points

	format:
		0: 16bit
		1: 8bit
		2: ADPCM 4bit
		3: ADPCM 4bit + loop (? dont know about this, since looping 
		                      seems to work fine for 2, but i haven't
				      tried diff start point than 0x0000 which
				      might require this setting since ADPCM
				      store delta instead of absolute values)

	addr_hi:
		highest 5 bits of waveform start address


00800004: (ch0_addr_lo)
+-----------------+
| 31-16 | 15-0    |
| n/a   | addr_lo |
+-----------------+

	addr_lo:
		lowest 16 bits of waveform start address


00800008: (ch0_loop_start)
+---------------+
| 31-16 | 15-0  |
| n/a   | start |
+---------------+

	start:
		starting sample of loop


0080000c: (ch0_loop_end)
+--------------+
| 31-16 | 15-0 |
| n/a   | end  |
+--------------+

	end:
		ending sample of loop


00800010: (ch0_adsr1)
+----------------------------------+
| 31-16 | 15-11 | 10-6 | 5   | 4-0 |
| n/a   | DR    | SR?  | n/a | AR  |
+----------------------------------+

	envelope register for amplitude

	DR:
		decay rate

	SR?:
		sustain rate (need to check by doing a key off, only guess)

	AR:
		attack rate


00800014: (ch0_adsr2)
+---------------------------------------+
| 31-16 | 15  | 14  | 13-10 | 9-5 | 4-0 |
| n/a   | n/a | ??? | ???   | ??? | ??? |
+---------------------------------------+

	envelope register for amplitude

	this register is seemingly kind of strange since
	the behaviour of 00800010 changes in odd ways
	when setting certain bits...will have to investigate
	more thoroughly later...

	unknown:
		set to 0x1f


00800018: (ch0_pitch)
+----------------------+
| 31-16 | 15-11 | 10-0 |
| n/a   | oct   | fns  |
+----------------------+

	controls the pitch of the waveform

	oct:
		calculated according to:

			[formula later]

	fns:
		calculated according to:

			[formula later]


0080001c: (ch0_lfo1)
+-----------------+
| 31-16 | 15-0    |
| n/a   | unknown |
+-----------------+

	envelope register for pitch

	unknown:
		set to 0x4210


00800020: (ch0_lfo2)
+-----------------+
| 31-16 | 15-0    |
| n/a   | unknown |
+-----------------+

	envelope register for pitch

	unknown:
		set to 0x0000


00800024: (ch0_pan_volume)
+------------------------------------+
| 31-16 | 15-12 | 11-8   | 7-5 | 4-0 |
| n/a   | ???   | volume | ??? | pan |
+------------------------------------+

	volume:
		aica level for this channel

	pan:	the position of this channel
		this is sort of confusing:

		0x00: almost in the middle
		0x0f: all panned to the left
		0x10: almost in the middle
		0x1f: all panned to the right


00800028: (ch0_volume2?)
+--------------------------+
| 31-16 | 15-8   | 7-0     |
| n/a   | volume | unknown |
+--------------------------+

	volume:
		logarithmic volume

	unknown:
		set to 0x24


0080002c: (ch0_???)
+-----------------+
| 31-16 | 15-0    |
| n/a   | unknown |
+-----------------+

	unknown:
		set to 0x1fff


00800030: (ch0_???)
+-----------------+
| 31-16 | 15-0    |
| n/a   | unknown |
+-----------------+

	unknown:
		set to 0x1fff


00800034: (ch0_???)
+-----------------+
| 31-16 | 15-0    |
| n/a   | unknown |
+-----------------+

	unknown:
		set to 0x1fff


00800038: (ch0_???)
+-----------------+
| 31-16 | 15-0    |
| n/a   | unknown |
+-----------------+

	unknown:
		set to 0x1fff


0080003c: (ch0_???)
+-----------------+
| 31-16 | 15-0    |
| n/a   | unknown |
+-----------------+

	unknown:
		set to 0x1fff


00800040: (ch0_???)
+-----------------+
| 31-16 | 15-0    |
| n/a   | unknown |
+-----------------+

	unknown:
		set to 0x0000


00800044: (ch0_???)
+-----------------+
| 31-16 | 15-0    |
| n/a   | unknown |
+-----------------+

	unknown:
		set to 0x0000


00800048: (ch0_???)
+-----------------+
| 31-16 | 15-0    |
| n/a   | unknown |
+-----------------+

	unknown:
		set to 0x0000

0080004c - 008007c: (not used, it seems)


[the other channels use the same layout as the above registers]

00800080 - 008000fc: (ch1)
00800100 - 0080017c: (ch2)
00800180 - 008001fc: (ch3)
00800200 - 0080027c: (ch4)
00800280 - 008002fc: (ch5)
00800300 - 0080037c: (ch6)
00800380 - 008003fc: (ch7)
00800400 - 0080047c: (ch8)
00800480 - 008004fc: (ch9)
00800500 - 0080057c: (ch10)
00800580 - 008005fc: (ch11)
00800600 - 0080067c: (ch12)
00800680 - 008006fc: (ch13)
00800700 - 0080077c: (ch14)
00800780 - 008007fc: (ch15)
00800800 - 0080087c: (ch16)
00800880 - 008008fc: (ch17)
00800900 - 0080097c: (ch18)
00800980 - 008009fc: (ch19)
00800a00 - 00800a7c: (ch20)
00800a80 - 00800afc: (ch21)
00800b00 - 00800b7c: (ch22)
00800b80 - 00800bfc: (ch23)
00800c00 - 00800c7c: (ch24)
00800c80 - 00800cfc: (ch25)
00800d00 - 00800d7c: (ch26)
00800d80 - 00800dfc: (ch27)
00800e00 - 00800e7c: (ch28)
00800e80 - 00800efc: (ch29)
00800f00 - 00800f7c: (ch30)
00800f80 - 00800ffc: (ch31)
00801000 - 0080107c: (ch32)
00801080 - 008010fc: (ch33)
00801100 - 0080117c: (ch34)
00801180 - 008011fc: (ch35)
00801200 - 0080127c: (ch36)
00801280 - 008012fc: (ch37)
00801300 - 0080137c: (ch38)
00801380 - 008013fc: (ch39)
00801400 - 0080147c: (ch40)
00801480 - 008014fc: (ch41)
00801500 - 0080157c: (ch42)
00801580 - 008015fc: (ch43)
00801600 - 0080167c: (ch44)
00801680 - 008016fc: (ch45)
00801700 - 0080177c: (ch46)
00801780 - 008017fc: (ch47)
00801800 - 0080187c: (ch48)
00801880 - 008018fc: (ch49)
00801900 - 0080197c: (ch50)
00801980 - 008019fc: (ch51)
00801a00 - 00801a7c: (ch52)
00801a80 - 00801afc: (ch53)
00801b00 - 00801b7c: (ch54)
00801b80 - 00801bfc: (ch55)
00801c00 - 00801c7c: (ch56)
00801c80 - 00801cfc: (ch57)
00801d00 - 00801d7c: (ch58)
00801d80 - 00801dfc: (ch59)
00801e00 - 00801e7c: (ch60)
00801e80 - 00801efc: (ch61)
00801f00 - 00801f7c: (ch62)
00801f80 - 00801ffc: (ch63)

00802000: (???)

00802004: (???)

00802008: (???)

0080200c: (???)

00802010: (???)

00802014: (???)

00802018: (???)

0080201c: (???)

00802020: (???)

00802024: (???)

00802028: (???)

0080202c: (???)

00802030: (???)

00802034: (???)

00802038: (???)

0080203c: (???)


00802040: (cd_pan_volume_left)
+---------------------------------------------+
| 31-16 | 15-13 | 12    | 11-8    | 7-5 | 4-0 |
| n/a   | n/a   | init? | volume  | n/a | pan |
+---------------------------------------------+

	volume:
		aica level volume for CD audio for left channel

	pan:	the position of the left channel
		this is sort of confusing:

		0x00: almost in the middle
		0x0f: all panned to the left
		0x10: almost in the middle
		0x1f: all panned to the right


00802044: (cd_pan_volume_right)
+---------------------------------------------+
| 31-16 | 15-13 | 12    | 11-8    | 7-5 | 4-0 |
| n/a   | n/a   | init? | volume  | n/a | pan |
+---------------------------------------------+

	volume:
		aica level volume for CD audio for right channel

	pan:	the position of the right channel
		this is sort of confusing:

		0x00: almost in the middle
		0x0f: all panned to the left
		0x10: almost in the middle
		0x1f: all panned to the right


00802890: (irq_timer_count)
+---------------+
| 31-16 | 15-0  |
| n/a   | count |
+---------------+

	count:
		(set to 0x00d4)


0080289c: (???)
+--------------+
| 31-16 | 15-0 |
| n/a   | ???  |
+--------------+


008028a4: (???)
+--------------+
| 31-16 | 15-0 |
| n/a   | ???  |
+--------------+


008028a8: (???)
+------------------------+
| 31-16 | 15-8 | 7-0     |
| n/a   | ???  | unknown |
+------------------------+

	unknown:
		set to 0x18


008028ac: (???)
+------------------------+
| 31-16 | 15-8 | 7-0     |
| n/a   | ???  | unknown |
+------------------------+

	unknown:
		set to 0x50


008028b0: (???)
+------------------------+
| 31-16 | 15-8 | 7-0     |
| n/a   | ???  | unknown |
+------------------------+

	unknown:
		set to 0x08


008028b4: (irq_mask)
+--------------+
| 31-16 | 15-0 |
| n/a   | ???  |
+--------------+


008028b8: (irq_request)
+--------------+
| 31-16 | 15-0 |
| n/a   | ???  |
+--------------+


008028bc: (irq_pending)
+--------------+
| 31-16 | 15-0 |
| n/a   | ???  |
+--------------+


008028b?: (irq_clear)
+--------------+
| 31-16 | 15-0 |
| n/a   | ???  |
+--------------+


00802d00: (irq_pend)
+--------------+
| 31-16 | 15-0 |
| n/a   | mask |
+--------------+


00802d04: (irq_clear)
+--------------+
| 31-16 | 15-0 |
| n/a   | pend |
+--------------+


00803bfc - 008033fc: (dsp registers)
+--------------+
| 31-16 | 15-0 |
| n/a   | ???? |
+--------------+


[this is mayhaps also accessible to the ARM7 but not tested]

a0702c00: (av_ctrl)
+-------------------------------------+
| 31-16 | 15-10 | 9-8   | 7-1 | 0     |
|  n/a  | n/a   | cable | n/a | reset |
+-------------------------------------+

	cable:
		type of video cable the display is to be set for:

		0: VGA
		1: ???
		2: RGB
		3: composite

	reset:
		0: normal
		1: reset ARM7