HuC6272 (KING)

Handles processing BG transfers, SCSI transfers, ADPCM transfers, and RAINBOW transfers.

Main RAM cannot be accessed directly, transfer data to KRAM with the KRAM interface

I/O Ports

Register (W)	0x600
Status (R)	0x600
Status 2(R)	0x602
Data (R/W)	0x604
Data 2(R/W)	0x606

Status

Bits	Description
0 ~ 6	Register selected
9	Busy
10	ADPCM buffer interrupt. Reading clears the interrupt.
11	HSync raster interrupt. "HuC6271 transfer control register's RINT bit (reg 0x40: bit1) reset and reset again to lead this state."
12	CD-ROM drive subcode interrupt. Reading clears this register's subcode or subcode register.
13	SCSI DMA end interrupt. Reading clears the SCSI DMA enable register.
14	SCSI block interrupt. SCSI bus reset occurs on a base phase mismatch. Reading clears SCSI reset interrupt register.
16 ~ 23	SCSI status. Just like register 0x05.
24 ~ 31	Sub-code

Register (SCSI-Related)

0x00 SCSI data

Bits	READ	WRITE
0 ~ 7	SCSI data	SCSI data

0x01 SCSI initiate command

Bits	READ	WRITE
0	Bus	Bus
1	ATN (?)	ATN (?)
2	Select	Select
4	Acknowledge	Acknowledge
7	Reset	Reset

0x02 SCSI mode

Bits	READ	WRITE
0	Sequential DMA	Sequential DMA
1	DMA	DMA

0x03 SCSI target command

Bits	READ	WRITE
0	I/O	I/O
1	C/D	C/D
2	Misc	Misc

0x05 SCSI bus status

Bits	READ	WRITE
0		"Once the DMA has written to the DMA mode, this register from the output of the SCSI bus. DMA starts."
1	Select
2	I/O
3	C/D
4	Misc
5	Request
6	Busy
7	Reset
16 ~ 23	SCSI -> CPU data	CPU -> SCSI data

0x06 SCSI Input data

Bits	READ	WRITE
0 ~ 7	Data

0x07 SCSI DMA

Bits	READ	WRITE
0 ~ 7	Clear SCSI interrupt	Initiate SCSI DMA

0x08 Subcode

Bits	READ	WRITE
0	Subcode	Subcode capture enable
1		Subcode interrupt enable
2
3
4
5
6
7

0x09 SCSI DMA start address

Bits	READ	WRITE
0 ~ 16	DMA transfer address	DMA transfer address
17	A/B	A/B

0x0A SCSI DMA transfer byte count

Bits	READ	WRITE
0	0
1 ~ 17	DMA transfer size	DMA transfer size

0x0B SCSI DMA control

Bits	READ	WRITE
0	DMA ended	DMA enable
1		DMA end interrupt enable
7		SCSI interface active level

Register (KRAM-Related)

0x0C KRAM read address (Word)

KRAM read address

Bits	Description
0 ~ 17	Address
18 ~ 27	Increment address
31	Page

0x0D KRAM write address (Word)

KRAM write address

Bits	Description
0 ~ 17	Address
18 ~ 27	Increment address
31	Page

0x0E KRAM read/write (Half)

When written, writes the data to the address in 0x0C then increases it.

When read, reads the data from the address in 0x0D then increases it.

0x0F KRAM page setup (Half)

Setup the pages of KRAM for KING

Bits	Description
0	KRAM page for SCSI
8	KRAM page for BG
16	KRAM page for RAINBOW
24	KRAM page for ADPCM

Register (BG-related)

0x10 BG mode (Half)

BG mode setting

Bits	Description
0 ~ 3	BG0 mode
4 ~ 7	BG1 mode
8 ~ 11	BG2 mode
12 ~ 15	BG3 mode

Mode values are like so:

0000	Unused
0001	4 palette
0010	16 palette
0011	256 palette
0100	64k color
0101	16M color
1001	4 palette block mode
1010	16 palette block mode
1011	256 palette block mode

0x12 Priority (Half)

BG prioritization

Bits	Description
0 ~ 2	BG0 priority
3 ~ 5	BG1 priority
6 ~ 8	BG2 priority
9 ~ 11	BG3 priority
12	BG0 rotation enable (wtf NEC)

Priority values are like so:

000	Hidden
001	Farthest back
010	Above back
011	Under first
100	Farthest forward
101 110 111	Prohibited

0x13 Microprogram address (Half)

Microprogram write address

0x14 Microprogram data (Half)

Microprogram data to write. Autoincrements register 0x13.

0x15 Microprogram control (Half)

Microprogram control.

Bits	Description
0	Microprogram running

0x16 Background scroll mode (Half)

Mode 0 is a single background area. Mode 1 is an endless background (looping?).

Bits	Description
0	BG0's scroll mode
1	BG1's scroll mode
2	BG2's scroll mode
3	BG3's scroll mode

0x20 BG0 BAT Address (Half)

BG0 BAT address. This is the address divided by 1024.

0x21 BG0 CG Address (Half)

BG0 CG address. This is the address divided by 1024.

0x22 BG0sub BAT Address (Half)

BG0sub BAT address. This is the address divided by 1024.

0x23 BG0sub CG Address (Half)

BG0sub CG address. This is the address divided by 1024.

0x24 BG1 BAT Address (Half)

BG1 BAT address. This is the address divided by 1024.

0x25 BG1 CG Address (Half)

BG1 CG address. This is the address divided by 1024.

0x26 BG2 BAT Address (Half)

BG2 BAT address. This is the address divided by 1024.

0x27 BG2 CG Address (Half)

BG2 CG address. This is the address divided by 1024.

0x28 BG3 BAT Address (Half)

BG3 BAT address. This is the address divided by 1024.

0x29 BG3 CG Address (Half)

BG3 CG address. This is the address divided by 1024.

0x2C BG0 size (Half)

Specify BG0 size

Bits	Description
0 ~ 3	Height
4 ~ 7	Width
8 ~ 11	Sub Height
12 ~ 15	Sub Width

Size values are like so:

Bits	Description
0011	8 px
0100	16 px
0101	32 px
0110	64 px
0111	128 px
1000	256 px
1001	512 px
1010	1024 px (only valid for BG0)

0x2D BG1 size (Half)

Specify BG1 Size. Same settings as 0x2C, except no sub size.

0x2E BG2 size (Half)

Specify BG2 Size. Same settings as 0x2C, except no sub size.

0x2F BG3 size (Half)

Specify BG3 Size. Same settings as 0x2C, except no sub size.

0x30 BG0 X scroll (Half)

The X coordinate of the upper-left corner of BG0.

0x31 BG0 Y scroll (Half)

The Y coordinate of the upper-left corner of BG0.

0x32 BG1 X scroll (Half)

The X coordinate of the upper-left corner of BG1.

0x33 BG1 Y scroll (Half)

The Y coordinate of the upper-left corner of BG1.

0x34 BG2 X scroll (Half)

The X coordinate of the upper-left corner of BG2.

0x35 BG2 Y scroll (Half)

The Y coordinate of the upper-left corner of BG2.

0x36 BG3 X scroll (Half)

The X coordinate of the upper-left corner of BG3.

0x37 BG3 Y scroll (Half)

The Y coordinate of the upper-left corner of BG3.

0x38 BG affine coefficient A (half)

Value is calculated like this, where a is the X zoom factor, and r is counter-clockwise rotation angle.

n = (1/a)*cos(r)

The value (n) is stored in an 8.8 fixed point format.

0x39 BG affine coefficient B (half)

Value is calculated like this, where b is the Y zoom factor, and r is counter-clockwise rotation angle.

n = -(1/b)*sin(r)

The value (n) is stored in an 8.8 fixed point format.

0x3A BG affine coefficient C (half)

Value is calculated like this, where a is the X zoom factor, and r is counter-clockwise rotation angle.

n = (1/a)*sin(r)

The value (n) is stored in an 8.8 fixed point format.

0x3B BG affine coefficient D (half)

Value is calculated like this, where b is the Y zoom factor, and r is counter-clockwise rotation angle.

n = (1/b)*cos(r)

The value (n) is stored in an 8.8 fixed point format.

0x3C BG affine center, X (half)

BG affine rotation center's X coordinate. Coordinate is relative to the center.

0x3D BG affine center, Y (half)

BG affine rotation center's Y coordinate. Coordinate is relative to the center.

Register (RAINBOW-related)

0x40 RAINBOW transfer control (half)

Bits	Description
0	Enable RAINBOW transfer
1	Interrupt on raster (specified by register 0x44) hit

0x41 RAINBOW KRAM transfer address (word)

Address of KRAM to transfer data to RAINBOW.

0x42 RAINBOW transfer start raster (half)

Start RAINBOW transfer at this raster count (0 ~ 261).

0x43 RAINBOW transfer block count (half)

Specifies the number of blocks of data RAINBOW transfers (1 block == 16 dots?) (0 ~ 31).

0x44 RAINBOW interrupt raster (half)

When the raster reaches this count, and if the interrupt bit in 0x40 is enabled, an interrupt is fired.

Register (ADPCM-related)

0x50 ADPCM control (half)

Bits	Description
0	Channel 0 play
1	Channel 1 play
2 ~ 3	Sampling rate	00 = 31.47kHz
		01 = 15.73kHz
		10 = 7.87kHz
		11 = 3.93kHz

0x51 ADPCM channel 0 control (half)

When in ring buffer mode, the buffer contents are looped. Sequential mode uses streaming (I think?)

Bits	Description
0	Buffer Mode	0 = Sequential
0	Buffer Mode	1 = Ring
1	End interrupt	0 = Disabled
1	End interrupt	1 = Allow
2	Intermediate interrupt	0 = Disabled
2	Intermediate interrupt	1 = Allow

0x52 ADPCM channel 1 control (half)

Just like 0x51 but for channel 1.

0x53 ADPCM status (half)

Reading contents of this register clears the flags.

Interrupt is level-triggered, and must be cleared in the handler to prevent an infinite loop.

Bits	Description
0	Channel 0 end interrupt
1	Channel 0 intermediate interrupt
2	Channel 1 end interrupt
3	Channel 1 intermediate interrupt

0x58 ADPCM channel 0 start address (half)

Starting address, divided by 256.

0x59 ADPCM channel 0 end address (word)

End address, no division. If in ring buffer mode, start address is reloaded when this is hit. If in sequential mode, playing is stopped and the play bit in register 0x50 is reset.

0x5A ADPCM channel 0 intermediate address (half)

Intermediate address, divided by 64. Used only if the intermediate interrupt bit in the channel's control is enabled.

0x5C ADPCM channel 1 start address (half)

Same contents as 0x58 for channel 1

0x5D ADPCM channel 1 end address (word)

Same contents as 0x59 for channel 1

0x5E ADPCM channel 1 intermediate address (half)

Same contents as 0x5A for channel 1

Microprogram

KING's BG is generated by a microprogram. The microprogram is a program in KRAM that describes how to output KING backgrounds.

The microprogram is 16 half words long. Addresses 0 ~ 7 are the A bank address (?). Addresses 8 ~ 15 is the B bank address (?).

Microprogramming opcode dissection

Bits	Description
0 ~ 2	Offset Offset of the data to access. If bit5 is set, this will always be 0.
3 ~ 4	Data access types	00 = CG data is accessed
		01 = BAT data associated to that CG data is accessed
		10 = BAT data is accessed
		11 = ???
5	Rotation flag This bit is 1 when you do rotation.
6 ~ 7	BG surface number Which BG will be operated upon.
8	NOP flag When this bit is 1, the opcode will still be parsed, but nothing will occur.

Limit

It is not possible to describe a microprogram that operates across banks.

16M color screen if it contains the rotation process can be done.

Non-rotating plane data width per 1dot 16bit or less. For example, 64k color screen and create a two-sided, three sides to create a color screen 256.

BG0 cannot be rotated.

Common Microprograms

16M color mode / 64k color mode microprogram

Code	Operation
0000	+0 from CG is accessed
0001	+1 from CG is accessed
0002	+2 from CG is accessed
0003	+3 from CG is accessed
0004	+4 from CG is accessed
0005	+5 from CG is accessed
0006	+6 from CG is accessed
0007	+7 from CG is accessed

256 color mode microprogram

Code	Operation
0000	+0 from CG is accessed
0001	+1 from CG is accessed
0002	+2 from CG is accessed
0003	+3 from CG is accessed

16 color mode microprogram

Code	Operation
0000	+0 from CG is accessed
0001	+1 from CG is accessed

4 color mode microprogram

Code	Operation
0000	+0 from CG is accessed

256 color block mode microprogram

Code	Operation
0010	+0 from BAT read
0100	NOP
0008	+0 from BAT CG is accessed
0009	+1 from BAT CG is accessed
000A	+2 from BAT CG is accessed
000B	+3 from BAT CG is accessed

16 color block mode microprogram

Code	Operation
0010	+0 from BAT read
0100	NOP
0008	+0 from BAT CG is accessed
0009	+1 from BAT CG is accessed

4 color block mode microprogram

Code	Operation
0010	+0 from BAT read
0100	NOP
0008	+0 from BAT CG is accessed

Plane rotation microprogram

Code	Operation
0020	Process rotation
0020	Process rotation
0020	Process rotation
0020	Process rotation
0020	Process rotation
0020	Process rotation
0020	Process rotation
0020	Process rotation

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