HPAVC/HPAVC CD-ROM.iso/VGADOC4B.ZIP/RAMDAC.TXT

Text File | 1995-09-29 | 84KB | 2,053 lines

RAMDACs

AcuMos:
ADAC1        15/16/24 bit.

Analog Devices:
ADV471       6bit DAC       15 overlay registers
ADV475       6bit DAC       15 overlay registers
ADV476       6bit DAC
ADV477       8bit DAC       15 overlay registers
ADV478       6/8bit DAC     15 overlay registers

ADV7129      True-Color 192bit pixel bus
ADV7160      True color 96bit pixel bus. 10bit DACs. HW cursor. PLL
ADV7162

ATI:
ATI68830     15/16/24bit    Up to 80 MHz    !
ATI68860     15/16/24bit    "Spectra" DAC for Mach64
ATI68875     15/16/24bit    Up to 135 MHz   ! Used in ATI Graphics Ultra +
                             and Pro.  Similar to TI34075
ATI68880                    Very similar to 68860

AT&T:
ATT20c40x   ??
ATT20c490    15/16/24 bit.  6/8 bit DAC.
ATT20c491    15/16/24 bit.  6/8 bit DAC w/gamma correction
ATT20c492    15/16/18 bit   6bit DACs. w/gamma correction
ATT20c493    15/16/18 bit   6bit DACs
ATT20c497    24bit          ?
ATT20c498    24bit          16bit pixel databus  !
ATT21c498    24bit          16bit pixel databus  ! What's the diff?
ATT22c498    24bit          16bit pixel databus  !


Avance Logic:
ALG1101      16-bit.        Appears to be different from the other HiColor
                            DACs.
ALG1201      24bit
ALG1301      24bit

Avasem:
AV3676       6bit DAC

Brooktree:
Bt458        8bit DAC       upto 135MHz. Not VGA compatible
Bt476        6bit DAC.
Bt477        6/8bit DAC
Bt478        6/8bit DAC.
Bt481        15/16bit
Bt482        15/16bit
Bt484        15/16/24bit    6/8bit DAC. Has hardware cursor.
Bt485        15/16/24bit    6/8bit DAC. Has hardware cursor.

Chrontel
CH8391
CH8398       15/16/24bit and Clock chip

Cirrus Logic
CL-GD5200    15/16/24 bit   Same as Acumos ADAC1

Diamond:
SS2410       15/24 bit.     OEM version of MUSIC MU9c1880

IBM:
RGB514       24bit.  144pin. HW cursor, 64bit pixel bus. Clock generator.
                             packed 24bit pixels
RGB524       24bit.  144pin. HW cursor, 64bit pixel bus. Dual clock generator
                             packed 24bit pixels
RGB525       24bit.  208pin. HW cursor, 64bit pixel bus. Clock generator
                             packed 24bit pixels
RGB526       24bit.  144pin. HW cursor, 64bit pixel bus. Dual clock generator
                             packed 24bit pixels
RGB528       24bit.  208pin. HW cursor, 128bit pixel bus. Dual clock generator
                             supports 24bit packed pixels
RGB530       24bit.  208pin. HW cursor. 96bit pixel bus. Clock generator,
                             10bit DACs and LUTs, window attribute table
RGB561       24bit.  304pin. HW cursor. 200bit pixel bus. Clock generator.
                             10bit DACs and LUTs
RGB624       24bit.  144pin. HW cursor, 64bit pixel bus, Dual clock generator
                             packed 24bit pixels, YUV to RGB conversion


ICS:
ICS5300      24bit          Combined RAMDAC & Clock chip
ICS5301
ICS5342      24bit          Combined RAMDAC & Clock chip

IC Works:
W30c498                     Similar to AT&T 20c498
W30c516      44pin          "ZoomDAC"

Inmos:
IMSG171
IMSG173
IMSG174
IMSG176      6bit DAC
IMSG178

MUSIC:
MU9C1710     6 bit DAC
MU9C4870     15/16 bit      Similar to Sierra "Mark 3".
MU9C1880     15/16/24bit    Same as SS24
MU9C4910     15/16/24bit
MU9C9910     15/16/24bit    As 4910, but with dual clock generator onchip
MU9C9750     6bit DAC       with onchip clock generator w/powerdown
MU9C9760     6bit DAC       with onchip clock generator
MU9C4160     15/16/24bit    16bit wide pixelbus
MU9C9160     15/16/24bit    As 4160, but with onchip clock generator

OAK:
OTI66        6bit DAC
OTI66HC      15/16bit       Similar to Sierra "Mark 3"

S3:
86c716 (SDAC)       Combined RAMDAC & Clockchip. Same as ICS 5300
86c708 (GenDAC)     Combined RAMDAC & Clockchip. Same as ICS 5342

Samsung:
KDA476       6bit DAC       Standard '476


SGS-Thompson:
STG1700      24bit          16bit pixel path.
STG1702      24bit  44pin   As 1700 + Supports "2 24bit pixels/3 VCLKs"
STG1703      24bit  68pin   As 1702 + onchip Clock Generator

Sierra Semiconductors:
Sierra  "Mark1":       Only works if the VGA controller can send a byte on
                       both the rising AND falling edge of the dot clock.
SC11481      15-bit.        6-bit DAC.   Overlay.
SC11486      15-bit.        6-bit DAC.
SC11488      15 bit.        6/8 bit DAC. Overlay.

Sierra  "Mark2":
SC11482      15-bit.        6-bit DAC.   Overlay.
SC11483      15-bit.        6-bit DAC.
SC11484      15-bit.        6/8 bit DAC. Overlay.

Sierra  "Mark3":
SC11485      15/16 bit.     6-bit DAC.   Overlay.
SC11487      15/16 bit.     6-bit DAC.
SC11489      15/16 bit.     6/8 bit DAC. Overlay.

SC15020      24bit          16bit pixel path
SC15021      24bit          16bit pixel path
SC15025      24 bit.
SC15026      24 bit.


TI:
TLC34058     8bit           upto 135MHz. Not VGA compatible
TLC34075     24bit          upto 135MHz
TVP3010      24bit          As 302x, but 32bit pixel path
TVP3020      24bit          64bit pixel path
TVP3025      24bit          As 3020 + Programmable Clock

Trident:
TKD8001      24bit

UMC:
UM70c171     Standard 6bit DAC
UM70c178     15/16 bit      Similar to Sierra "Mark 3"
UM70c188     24bit

Winbond:
W82c476      6bit DAC       Standard '476
W82c478      6/8bit DAC     Standard '478
W82c490      15/16/24bit    Very close to the AT&T20c492


15-bit modes have 5 bits of each basic color:
bit  0- 4 blue.
     5- 9 green.
    10-14 red.
The pixel is stored in two bytes in Intel style (little endian).

16-bit modes have 5 bits of red and blue, and 6 bits of green:
bits 0- 4  blue.
     5-10  green.
    11-15  red.
The pixel is stored in two bytes in Intel style (little endian).

24-bit modes have 8 bits of each basic color:
bits 0- 7  blue.
     8-15  green
    16=23  red.
The pixel is stored in three bytes in Intel style (little endian).



The DACs are addressed on port 3C6h-3C9h. Advanced DACs have 1 or 2 extra
address lines (RS2 and RS3). These may be controlled from high address bits
(A10-A15) (Compaq or Weitek cards) or from registers (S3, ATI....).
In the following the DAC registers are named REGxx as follows:

            I/O:     RS2:     RS3:
REG00       3C8h      0        0
REG01       3C9h      0        0
REG02       3C6h      0        0
REG03       3C7h      0        0
REG04       3C8h      1        0
REG05       3C9h      1        0
REG06       3C6h      1        0
REG07       3C7h      1        0
REG08       3C8h      0        1
REG09       3C9h      0        1
REG0A       3C6h      0        1
REG0B       3C7h      0        1
REG0C       3C8h      1        1
REG0D       3C9h      1        1
REG0E       3C6h      1        1
REG0F       3C7h      1        1



Many of these DACs can access REG06 using only the 4 standard DAC addresses
(3C6h-3C9h) by reading 3C6h 4 or 5 times, then REG06 can be accessed at 3C6h.

  Type:

  "1r/w"   Read 3C6h 4 times, then the next read or write of 3C6h will access
           the command register.


Forcing HiColor DACs into command mode:
Note: This works on the Sierra, ATT, Winbond DACs and clones, not on the
 Brooktree or TI DACs, also the MUSIC DACs will require an extra read of 3C6h.

procedure dactocomm;   {switches DAC to command register}
var x:word;
begin
  x:=inp($3C8);    {clear old state}
  x:=inp($3C6);
  x:=inp($3C6);
  x:=inp($3C6);    {Read $3C6 4 times.}
  x:=inp($3C6);
end;

Now reads and writes to $3C6 will access the command register. Depending on
the DAC type you may have multiple read/writes, one write/multiple reads or
one read/write of the command register before it switches back to the PEL
register. Any access to $3C7-$3C9 will switch back to the PEL mask register.


Forcing HiColor DACs into normal mode:

procedure dactopel;  {switches DAC back to normal mode}
var x:word;
begin
  x:=inp($3C8);
end;




HiColor DACs:     (Sierra SC1148x, MUSIC MU9C4870, OAK OTI66HC, UMC UM70C178)

REG04 (R/W):  Overlay RAM Write Address               (SC11481/2/4/5/8/9 only)
bit 0-3  Write index for the Overlay registers.

REG05 (R/W):  Overlay RAM                             (SC11481/2/4/5/8/9 only)
bit 0-5  Data port for the overlay registers. Works like the PEL data register
         (3C9h) except that the overlay registers are accessed and the Overlay
         Address registers are used for indexes.
Note: on the SC11484/8/9 the Color Look-up Table and the overlay registers are
      24bits wide (rather than 18bits) if the 8/6 pin is high.

REG06 (R/W):  Command Register
bit   0  (SC11487) (R) Set if bits 5-7 is 1 or 3, clear otherwise
    3-4  (SC11487) Accesses bits 3-4 of the PEL Mask registers (REG02)
      5  (not SC11481/6/8)
         If set two pixel clocks are used to latch the two bytes
         needed for each pixel. Low byte is latched first.
         If clear the low byte is latched on the rising edge of the
         pixel clock and the high byte is latched on the falling edge.
         Only some VGA chips (ET4000 and C&T655x0) can handle this.
      6  (SC11485/7/9, OTI66HC, UM70C178) Set in 16bit (64k) modes (Only valid
           if bit 7 set). On the SC11482/3/4 this bit is read/writable, but
           has no function. On the SC11481/6/8 this bit does not exist.
      7  Set in HiColor (32k/64k) modes, clear in palette modes.
Note:  This register can also be accessed at 3C6h by reading 3C6h four times,
       then all accesses to 3C6h will go the this register until one of the
       registers 3C7h, 3C8h or 3C9h is accessed.

REG07 (R/W):  Overlay RAM Read Address              (SC11481/2/4/5/8/9 only)
bit 0-3  Read index for the Overlay registers.



Analog Devices ADV7160,ADV7162 True-Color Video RAM-DAC:
The ADV716x DACs are not really VGA compatible, but with proper initialisation
palette writing and the PEL register can be simulated.
REG00 W(R/W):  Address Register
bit 0-10  Controls the index read or written at REG01 or REG02.
          Regardless of the bus width this register is accessed by two 8bit
          reads or writes at this address, low byte first.

REG01


REG02 Control Registers
REG02 index 3 (R):  ID Register
bit  0-7  76h for the ADV7160, 79h for the ADV7162

REG02 index 4 (R/W):  Pixel Mask Register
bit  0-7  The pixel inputs (R, G and B) are anded with this value. Set to FFh
          for normal operation.

REG02 index 5 (R/W):  Command Register 1
bit    0  Calibration Control. If set the LOADIN/LOADOUT synchronization
          circuit is calibrated on every vertical sync (REG03 bit 5 must be 0)
       1  Test Mode Control. Enable test mode if set
       2  Should be set to 0
       3  Hi-Byte Control. If set the high byte of the Address Register
          (REG00) is accessible, if clear it is not (ADV7150 compatible).
     4-5  PS Function Control. Controls how the PS0/1 inputs are used.
           0: Palette Select Mode. The PS0/1 inputs selects between 4 devices
          by comparing with REG03 bits 6-7 on a pixel by pixel base,
           1: (ADV7160) Bypass Mode. PS1 switches between Palette Mode and
          Bypass Mode on a pixel by pixel basis. Bits 6-7 controls the Bypass
          Mode. Bypass mode should not be selected in Command Register 2
          (REG02 index 6) and by this field at the same time, 2: Overlay Mode.
          PS0/1 select one of the three overlay colors (PS0/1 = 0 for pixel
          data), 3: Ignore PS Inputs. The PS0/1 inputs are completely ignored.
     6-7  Bypass Color Mode Control. Controls the bypass mode switching.
           0: 15bit bypass, 1: 16bit bypass, 2: 24bit bypass

REG02 index 6 (R/W):  Command Register 2
bit  0-1  Should be set to 0
       2  /SYNC Recognition on Green. If set the /SYNC input is encoded on the
          IOG output.
       3  Pedestal Enable Control. Set for a 7.5 IRE blanking pedestal, clear
          for a 0 IRE pedestal.
     4-7  True-Color/Bypass/Pseudo-Color Mode Control. 0: 8bit Pseudo Color
          on R0-7, 4: 8bit Pseudo Color on G0-7, 8: 8bit Pseudo Color on B0-7,
           9: 16bit Bypass Mode on G0-7 + R0-7, 10: 15bit Bypass Mode on G0-7
           + R0-6, 11: 16bit True Color Mode on G0-7 + R0-7, 12: 15bit True
          Color Mode on B3-7 + G3-7 + R3-7, 13: 15bit True Color Mode on G0-7
           + R0-6, 14: 24bit True Color Mode, 15: 16bit Bypass Mode

REG02 index 7 (R/W):  Command Register 3
bit  0-1  PROGCKOUT Frequency Control. Determines the PROGCKOUT output clock
          frequency relative to the pixel clock (CLOCK). 0: CLOCK/4,
           1: CLOCK/8, 2: CLOCK/16, 3: CLOCK/32
     2-4  /BLANK Pipeline Delay Control. Controls the delay of the /BLANK
          signal (in addition to the overall device pipeline delay Tpd).
          Adds N * LOADOUT to the /BLANK delay.
       5  Should be set to 0
     6-7  Pixel Multiplex Control. 0: 1:1 MUXING - LOADOUT = CLOCK, 1: 2:1
          MUXING - LOADOUT = CLOCK/2, 2: 8:1 MUXING - LOADOUT = CLOCK/8
          (Pseudo Color Mode only), 3: 4:1 MUXING - LOADOUT = CLOCK/4,

REG02 index 8 (R/W):  Command Register 4
bit    0  HDTV Sync Control. If set the /TRISYNC input is encoded enabling a
          Tri-Level Sync output.
       1  /SYNC Recognition Control on Red. If set the /SYNC input is encoded
          on the IOR output.
       2  /SYNC Recognition Control on Blue. If set the /SYNC input is encoded
          on the IOB output.
     3-4  Gain Control. Selects the Video Standard used.
          Value: DAC Gain: Video Standard            Black to White current:
            0      3996    RS343A, Sync & Pedestal       660mV  17.62mA
            1      4224    RS343A, Sync, No Pedestal     699mV  18.63mA
            2      4311    RS343A, No Sync, No Pedestal  714mV  19.05mA
            3      5592    RS170,  Sync & Pedestal       925mV  24.67mA
       5  Signature Clock Control. Enables the Signature Analyser if set
       6  Signature Reset. To reset the Signature Analyser write 0, then 1
          to this field.
       7  Signature Acquire. Enables Signature Acquisition if set

REG02 index 9 (R/W):  PLL Command Register
bit    0  PLL Control. Enables the PLL if set
       1  RSEL Bit Control. When set the PLL Reference Divider is in units of
           2, if clear in units of 1. See REG02 index 0Ch for details.
       2  VSEL Bit Control. When set the PLL Feedback Divider is in units of
           2, if clear in units of 1. See REG02 index 0Fh for details.
       3  Should be set to 0
     4-5  Output Divide Control. Selects the Post divider for the VCO
           0: VCO/1, 1: VCO/2, 2: VCO/4, 3: VCO/8
     6-7  PLL S Control. The lower two bits of the PLL Feedback value.
          See REG02 index 0Fh for details.

REG02 index 0Ah (R):  Status Register
bit    0  Set if either of the IOR,IOG or IOB outputs exceeds the internal
          voltage of the /SENSE comparator circuit

REG02 index 0Bh (R):  Revision Register
bit  0-?  Silicon Revision Code.

REG02 index 0Ch (R/W):  PLL R Register
bit  0-6  Controls the PLL Reference Divider value together with the RSEL bit
          (index 9 bit 1). If this field is set to 0 the PLL stops.
          The effective value is: (1+RSEL)*(This_Field+2).
          This allows all values from 3-129 and all even values from 130-258.

REG02 index 0Dh (R/W):  Command Register 5
bit  0-5  Should be set to 0
       6  Set to enable the internal PLL, clear to disable it
       7  Should be set to 0

REG02 index 0Fh (R/W):  PLL V Register
bit  0-6  Controls the PLL Feedback Divider value together with the VSEL bit
          (index 9 bit 2). If this field is set to 0 the PLL stops.
          The effective value is: (1+VSEL)*(4*(This_Field+2)+ S)
          where S is the value from REG02 index 0Ch bits 6-7.
          This allows all values from 12-519 and all even values from 520-1038

REG02 index 10h (R):  Signature Red Register
REG02 index 11h (R):  Signature Blue Register
REG02 index 12h (R):  Signature Green Register
REG02 index 13h (R):  Signature Misc Register

REG02 index 200h W(R/W):  Cursor X Register
bit 0-15  The X coordinate of the cursor as a 2's complement (-4096 to 4095).
Note: Low byte in index 200h, High byte in index 201h
Note: When accessing the cursor X/Y registers (index 200h to 203h) the index
      register autoincrements with each access. These registers must be
      updated in the order 200h,201h,202h and then 203h

REG02 index 202h W(R/W):  Cursor Y Register
bit 0-15  The Y coordinate of the cursor as a 2's complement (-4096 to 4095).
Note: Low byte in index 202h, High byte in index 203h
Note: When accessing the cursor X/Y registers (index 200h to 203h) the index
      register autoincrements with each access. These registers must be
      updated in the order 200h,201h,202h and then 203h

REG02 index 204h (R/W):  Cursor Control Register
bit  0-1  Cursor Mode Control. 1: X11 cursor, 2: XGA cursor
          Pattern:    X11 cursor:        XGA cursor:
             0        Transparent        Color 1
             1        Transparent        Color 2
             2        Color 1            Transparent
             3        Color 2            Bit-Wise Complement (XOR cursor)
       2  Cursor Enable. Enables the cursor if set
       3  Interlace Control. Set for interlaced modes.
     4-7  Should be set to 0

REG02 index 303h (R/W):  Color 2


REG02 index 304h (R/W):  Color 1

REG02 index 400h-7FFh (R/W):  Cursor Image
bit  0-7  The 64x64 cursor image is stored in these 1024 bytes with 4 2bit
          "pixels" per index. Index 400h holds the 4 leftmost pixels of the
          first (topmost) line, index 40Fh the 4 rightmost and index 7FFh the
          4 rightmost pixels of the last line.

REG02 index 0-2, 0Eh, 14h and 15h are labeled as "Test Registers"

REG03 (R/W):  Mode Register
bit    0  Reset Control. To reset the pixel port sampling sequence to start
          with port A, write 1, then 0 and finally 1 to this bit.
       1  RAM-DAC Resolution Control. If set the LUT and DACs are 10bits, if
          clear LUT and DACs are 8bits (lower 2 inputs to the 10bit DACs are
          forced to 0).
       2  MPU Data Bus Width. If set the MPU interface is 10 bits wide
     3-4  Operational Mode Control. 0 for normal operation
       5  Calibrate LOADIN. To calibrate the LOADIN/LOADOUT synchronization
          circuit write 0, then 1 to this bit. Should be 0 for normal
          operation.
     6-7  Palette Select Match Bits Control. If Command Register 1 (REG02
          index 5) bits 4-5 is 0 the PS0-1 bits are compared with these two
          bits on a pixel per pixel base allowing realtime switching between
          up to 4 devices




ATI 68860/68880 Truecolor DACs:
REG08 (R/W):
bit 0-?  Always 2 ??

REG0A (R/W):
bit 0-?  Always 1Dh ??

REG0B (R/W):  (GMR ?)
bit 0-7  Mode. 82h: 4bpp, 83h: 8bpp, A0h: 15bpp, A1h: 16bpp, C0h: 24bpp,
          E3h: 32bpp  (80h for VGA modes ?)

REG0C (R/W):  Device Setup Register A
bit   0  Controls 6/8bit DAC. 0: 8bit DAC/LUT, 1: 6bit DAC/LUT
    2-3  Depends on Video memory (= VRAM width ?) . 1: Less than 1Mb, 2: 1Mb,
           3: > 1Mb
    5-6  Always set ?
      7  If set can remove "snow" in some cases (A860_Delay_L ?) ??




AT&T 20c49x,Winbond W82c490 Truecolor DACs:

REG06 (R/W):  Command Register
bit   0  (W82c490, some ATTs) Power Down Enable. If set the DACs and video
          multiplexers are powered down. The CPU interface is still working.
      1  (490,491) In mode 0 this bit when set selects 8bit DACs, when clear
            6bit DACs.
    2-4  Exists, but appears to have no function ?
    5-7  Mode:  0-3: Palette, 4: 15bit (32k) the two bytes are latched on
         opposite edges of the dotclock (similar to SC11486), 5: 15bit (32k),
           6: 16bit (64k), 7: 24bit (16m)
Note: This register can also be accessed by reading REG02 4 times, then the
      next read or write of REG02 will access this register. Any access of
      REG00, REG01 or REG03 will terminate the access to this register. The
      register can only be read or written once before the DAC is returned to
      normal mode (DAC type 4-1r1w).




AT&T 20c498,21c498,22c498 Truecolor DACs (Also IC Works?):
REG06 (R/W):  Command Register
bit 0,2  (22c498) Clockmode for Mode 2 (2 8bit pixels/VCLK). 0: Clock < 22.5
            MHz, 1: Clock < 45 MHz, 2: Clock >= 45 MHz
      1  In palette modes this bit when set selects 8bit DACs, when clear 6bit
         DACs.
    4-7  Mode: 0: 8bit 1VCLK/pixel, 1: 15bit 1VCLK/pixel, 2: 8bit (2 pixels/
          VCLK), 3: 16bit 1VCLK/pixel, 5: 24/32bit 2VCLKs/pixel, 6: 16bit
          2VCLKs/pixel
Note:  This register can also be accessed at REG02 by reading REG02 four times,
       The fifth read will access of 3C6h will access this register. Only one
       read or write will be allowed (DAC type 4-1r1w2i), the 6th read returns
       84h and the 7th returns 98h (don't know about the 20c498).




Avance Logic ALG1201 Truecolor DAC:
REG06 (R/W):  "Hidden Command register"
bit 5-7  Mode. 5: 15bit, 6: 16bit, 7: 24bit
Note: This register can also be accessed by reading REG02 4 times, then the
      next read or write of REG02 will access this register. Any access of
      REG00, REG01 or REG03 will terminate the access to this register. The
      register can only be read or written once before the DAC is returned to
      normal mode (DAC type 4-1r1w).




BrookTree Bt477:
REG06 (R/W):
bit   0  DAC powerdown. If set the DAC powers down
      1  DAC Width. If set the DAC and palette registers are 8bit wide, if
          clear only 6bit wide (as std VGA).
      5  IRE control ?? seems to affect the output intensity ?




BrookTree Bt481/482:

REG00 index 0 (R/W):  Ind Pixel Mask

REG00 index 1 (R/W):  Overlay Mask

REG00 index 2 (R/W):  Command Register B
bit    0  Set to power down the DAC (Sleep mode).
       1  DAC Width. If set the DAC and palette registers are 8bit wide, if
          clear only 6bit wide (as std VGA).
       2  Sync on Red if set
       3  Sync on Green if set
       4  Sync on Blue if set
       5  Set for 7.5 IRE, clear for 0.0 IRE pedestal (affects DAC range).
       6  Enables the Overlay registers if set

REG00 index 3 (R/W):  Cursor Register                                    (482)
bit  0-1  Cursor type. 0: disabled, 1: 3-color, 2: Windows, 3: X11 style
       2  Cursor Op disabled if set?
       3  If clear reads/writes to REG04,REG05,REG07 will access the cursor
          palette, if set the cursor pattern data will be accessed instead.
       4  Set in interlaced modes
       5  Selects External cursor if set

REG00 index 4 W(R/W):  Cursor X                                          (482)
bit 0-11  Cursor X position

REG00 index 6 W(R/W):  Cursor Y                                          (482)
bit 0-11  Cursor Y position
Note: the indexed DAC registers are accessed by setting bit 0 of REG06. Then
      REG00 is the index register and REG02 is the data register.

REG04 (R/W):  Cursor Write Address                                       (482)
bit 0-1?  Selects the palette register which will be written at REG05
            0: Overscan, 1: Cursor Background, 2: Cursor Foreground

REG05 (R/W):  Cursor RAM Data                                            (482)
bit  0-7  Cursor palette data
Note: If REG00 index 3 bit 3 is clear this works like the palette address&data
      registers at REG00,REG01®03 except that a separate palette is
      accessed. Each read/write of this register will increment first through
      the red,green,blue sequence and then the Address register (REG04/REG07).
      If REG00 index 3 bit 3 is set REG04/REG07 are the lower 8 bits of the
      index into the 1024 byte palette pattern RAM, which will increment for
      each access to this register.

REG06 (R/W):  Command Register A
bit    0  If set the Bt481/2 indexed DAC registers can be accessed by setting
          REG00 to the index and reading or writing the data at REG02.
     4-7  Mode. 0: Palette, 8: 15bit (Dual edge), 9: 24bit (Dual edge),
            Ah: 15bit (32K), Ch: 16bit (Dual edge), Eh: 16bit (64K),
            Fh: 24bit (16m). The Dual edge modes transfers data on both the
          rising and falling edges of the pixel clock.
Note:  This register can also be accessed at REG02 by reading REG02 four
       times. Then the command register can be read or written at REG02.
       This access will be terminated by any access to REG00, REG01 or REG03
       or after a write to the command register (DAC type 4-Nr1w).

REG07 (R/W):  Cursor Read Address                                        (482)
bit 0-1?  Selects the palette register which will be read at REG05




BrookTree Bt484, Bt485, AT&T 20c504/5 Truecolor DACs:
The 485 and 505 has the extra register at REG0A and supports 64x64 cursor
The 484 & 504 appears to be limited to 110MHz, the 485/505 to 135MHz

REG04 (R/W):  Cursor/Overscan Write Address
bit 0-7  The PEL data register (0..255) to be written to REG05.
Note: After writing the 3 bytes at REG05 this register will increment, pointing
      to the next data register.

REG05 (R/W):  Cursor/Overscan Data
bit 0-5  Color value
Note:  Each read or write of this register will cycle through first the
       registers for Red, Blue and Green, then increment the appropriate
       address register.
Note: the registers REG04,REG05,REG07 works like the normal REG00,REG01,REG03
      registers, except that a separate set of palette registers (16 overlay
      registers ?) are being accessed.
      Index 00h  Overscan color
            01h  Cursor Color 1 (Background)
            02h  Cursor Color 2 (Foreground)
            03h  Cursor Color 3
Note: if the DAC is in 6bit mode (REG06 bit 1 is 0) the 2 upper bits of the
      cursor colors are ignored.

REG06 (R/W):  Command Reg 0
bit   0  Power Down. If set the DACs and RAM power is turned off, but the RAM
         still retains data, if clear the RAMDAC is operating normally
      1  Set if DAC and palette registers are 8bit DACs, clear if 6bit.
      2  Sync on Red if set
      3  Sync on Green if set
      4  Sync on Blue if set
      5  Set for 7.5 IRE pedestal, clear for 0.0 IRE.
      6  Disables internal clocking if set
      7  (485,505) Enable CR3. If clear the Status register is present at
          REG0A, if set 3C8h determines which register is present at REG0A:
            00h    Status Register
            01h    Command Register 3

REG07 (R/W):  Cursor/Overscan Read Address
bit 0-7  The PEL data register (0..255) to be read from REG05.
Note: After reading the 3 bytes at REG05 this register will increment,
      pointing to the next data register.

REG08 (R/W):  Command Reg 1
bit    0  In 15/16bit 1:1 mode selects the pixel port (A-B or C-D) to take
          pixel data from. Clear for A-B, set for C-D. See bit 1.
       1  PORTSEL. In 15bit 1:1 mode (bit 2 set & bit 3 clear), this bit if
          set causes pin P7D (most significant bit of the C-D port) to select
          whether the 15bit pixel data is taken from port A-B or port C-D,
          thus allowing real-time switching between video sources.
       2  SPARSE. Set if 16bit data is 1:1, clear if it is muxed 2:1
       3  Set in 5/6/5 mode, clear in all other modes
       4  If set decodes True-color pixel data (5/5/5, 5/6/5 or 8/8/8 mode),
          directly, if clear each component (R-G-B) of the pixel data is used
          is used as a separate index to the palette RAM for the specific RGB
          component, allowing non-linear scales (gamma correction) for each
          color-component. REG09 bit 2 controls the indexing.
     5-6  Bits per pixel. 0: 24, 1: 15/16, 2: 8, 3: 4

REG09 (R/W):  Command Reg 2
bit  0-1  Cursor mode. 0: Disabled, 1: 3-Color, 2: Windows, 3: X11 Style
       2  Sparse or Contigous Indexing. In Look-up True-color modes (REG08 bit
          4 clear) selects whether each color component is shifted right or
          left before being used as an index to the palette. If set the pixel
          data is treated as the least significant bits of the index
          (Contigous index), if clear as the most significanty bits (Sparse
          index).
       3  Set in interlaced modes (used for the cursor).
       4  Selects input clock. 0: PCLK0, 1: PCLK1
       5  If clear the dac takes data from the VGA port and each byte is a one
          byte palette index regardless of the state in Command Register 1, if
          set pixel data is taken from pixel ports A-D and data format is
          controlled by Command Register 1
       6  Test Path enabled if set.
       7  SCLK (Video shift clock) disabled if set.

REG0A (R):  Status Reg
bit 4-7  Product ID ?
           4: AT&T20c504, 0Dh: AT&T20c505, 8-Bh: Bt484/5
Note: The two registers at REG0A are selected by bit 7 of REG06.

REG0A (R/W):  Command Reg 3                                   (485,505 only)
Bit  0-1  Bits 8-9 of the Palette Write Address (3C8h)
       2  Set if using 64x64 cursor, clear if 32x32 cursor.
       3  If set the Clock Doubler is enabled and the input clock is doubled.
Note: The two registers at REG0A are selected by bit 7 of REG06.
      This register does not exist on the Bt484

REG0B (R/W):  Cursor Ram Data
bit  0-7  Data port for the Hardware Cursor Map.
          There are either 2 128byte (32x32bit) or 2 512 byte (64x64bit) maps
          depending on REG0A bit 2. The first is the cursor image and the
          second is the cursor shape.
          To update the cursor map, write the start address to REG00and start
          writing to this register. The index will increment for each byte.

REG0C W(R/W):  Hardware Cursor X-position
bit 0-11  The X-position of the rightmost pixel of the hardware cursor

REG0E  W(R/W):  Hardware Cursor Y-position
bit 0-11  The Y-position of the lower scanline of the hardware cursor




Chrontel CH8391 and CH8398:
REG04 (R/W):  Clock RAM Write Address
bit  0-?  Selects the register that is writable at REG05. The first write
          accesses the low byte of the register and the second the high byte.
Note: Reading this register 4 times will cause the next access of this
      register to go to the "Hidden Clock" register.

REG04 (R/W):  Clock Select Register
bit  0-3  Selects the Video Clock.
     4-6  Selects the Memory Clock
       7  Frequency hold. If set the video and memory clock selects in bits
           0-6 are ORed with the actual inputs from the clock select pins
Note: This register is accessed6 by reading REG04 4 timers first.

REG05 (R/W):  Clock RAM Data Register
Note: each indexed register addressed here is 16bit wide and thus must be
      read/written as two bytes, low byte first.

REG05 index 00h-0Fh W(R/W):  Video Clock Select 0-15
bit  0-7  N. Numerator. Effective value (n) is N+8. The following N values
           may give unstable output: 0-7, 10-15, 19-23, 28-31, 37-39, 46-47
           and 55.
    8-13  M. Denominator. Effective value (m) is M+2. It is recommended to
           use N<11 for best clock performance
   14-15  K. Clock Divider. Effective divider (k) is: 0: 1, 1: 2, 2: 4, 3: 8
The resulting clock is: ref*n/(m*k) where ref is the reference clock, usually
 14.31818MHz and n,m and k are the effective (as opposed to coded) factors
Note: The CH8398 apparently has Video Clock 0 hardcoded as 25.175MHz and
      Video Clock 1 hardcoded as 28.322. The CH8391 does not.

REG05 index 10h-17h W(R/W):  Memory Clock Select 0-7
Probably same coding as the Video Clocks.

REG06 (R/W):  Control Register (CH8391)
bit    0  Power Down if set
       1  If set the DAC and palette registers are 8bit wide (256 colors of
           16Mcolors), if clear 6bit (256 colors of 256K colors)
     5-7  Color mode. 0: Palette, 5: 15bit, 6: 16bit, 7: 24bit
Note: This register can also be accessed by reading 3C6h 4 times in a row.
      The 4th read will return the chip ID (B3h for the CH8391) and the 5th
      read or write will access this register ("1r/w" type Cmd register).

REG06 (R/W):  Control Register (CH8398)
bit    0  Power Down if set
       2  Always set ??
     4-7  Color mode. 0: Palette, 1: 15bit, 3: 16bit, 5: 24bit, 6: 16bit,
           7: 24bit, 11: 24bit, 12: 15bit
Note: This register can also be accessed by reading 3C6h 4 times in a row.
      The 4th read will return the chip ID (C0h for the CH8398) and the 5th
      read or write will access this register ("1r/w" type Cmd register).

REG07 (R/W):  Clock RAM Read Address
bit  0-?  Selects the register that is readable at REG05. The first read
          accesses the low byte of the register and the second the high byte.




Cirrus Logic 542x/3x internal DAC.
 - How close is this to the Cirrus Logic CL-GD5200 & Acumos ADAC1 ?
REG02 (R/W):  Hidden DAC Register
bit  0-3  Extended Mode Select. If bit 6 and 7 are both set this field
          selects the DAC mode:
              0:  5-5-5 15bit Sierra HiColor
              1:  5-6-5 16bit "XGA" HiColor
              5:  (5422+) 8-8-8 24bit TrueColor. This mode also exists on the
                    5420 rev1, but is not documented.
            6/7:  (5428+) DAC Power-down
              8:  (5428+) 8bit Greyscale.
              9:  (5428+) 3-3-2 8bit RGB
       4  32K Color Control. If set bit 15 (MSB) of a 15bit pixel selects
          whether the pixel is HiColor(bit 15 = 0) or palette data(bit 15 = 1,
          bit 0-7 is the palette index). This bit only has effect in 5-5-5
          15bit modes.
       5  Clocking Mode. If set Clocking Mode 2 will be selected and data will
          only be latched on the rising edge of DCLK, if clear Clocking Mode 1
          will be selected and data will be latched on both the rising edge
          (low byte) and falling edge (high byte) of DCLK. This bit only has
          effect in 15/16 bit modes as all other modes will use Clocking Mode
          2. Clocking Mode 1 should only be used for externally supplied DCLK
          and pixel data.
       6  Enable ALL Extended Modes. If bit 7 is set and this bit is clear the
          DAC is in 5-5-5 15bit Sierra HiColor mode, if both bit 7 and this
          bit are set bits 0-3 determines the DAC mode.
       7  Enable 5-5-5 Mode. If set the DAC is in an advanced mode, depending
          on the other bits in this register, if clear the DAC is in VGA
          compatible palette mode.
Note: This register is accessed by reading REG02 four times to unlock this
      register, then the next read or write of REG02 will access this register.
      After reading or writing this register the register is locked and this
      register can only be accessed be redoing the 4 reads of REG02 etc. Any
      access to REG00,REG01,REG03 will also lock this register. The 5428 is the
      exception where reads of this register will NOT lock it.
Note: When REG02 is 0FFh the access to this register described above does
x      not always work.
Note: This register does not exist on the 5401/5402 and the 5420 rev A.




IBM RGB514, RGB524, RGB525, RGB528 Truecolor DAC w/PLL:
REG04 W(R/W):  Index
bit  0-?  Selects the indexed register that will be accessed by the next read
          or write of REG06. If REG07 bit 0 is set this index is
          autoincremented by each access of REG06.

REG06 index 00h (R):  Rev
bit  0-7  Revision. F0h for the RGB524, ? for the RGB514, RGB525,RGB528

REG06 index 01h (R):  Id
bit  0-7  Chip ID. 2 for the RGB524, ? for the RGB514,RGB525,RGB528

REG06 index 02h (R/W):  Misc Clock
bit    0  Set for internal (PLL) clock ??
       1  Set for double clock

REG06 index 03h (R/W):  Sync
REG06 index 04h (R/W):  Hsync Pos
bit  0-3  Hsync Position ?

REG06 index 05h (R/W):  Power Management
REG06 index 06h (R/W):  DAC Options
bit    1  Fast slew if set ?
       3  Sync on Green if set

REG06 index 07h (R/W):  Palette Control
REG06 index 08h (R/W):  System Clock                             (Not RGB525?)
REG06 index 0Ah (R/W):  Pixel Format
bit  0-2  Pixel format. 3: 8bpp, 4: 15/16bpp, 6: 32bpp

REG06 index 0Bh (R/W):  8bpp
REG06 index 0Ch (R/W):  16bpp
bit    1  Set for 16bpp (5:6:5), clear for 15bpp (5:5:5)

REG06 index 0Dh (R/W):  24bpp
REG06 index 0Eh (R/W):  32bpp
REG06 index 10h (R/W):  PLL Control 1
bit    0  Set to use 8 internal clocks with separate numerators, clear to
          use 16 internal clocks with a common numerator (index 14h).
     1-2  Set to 1 ??

REG06 index 11h (R/W):  PLL Control 2
bit  0-3  Selects the PLL clock used (0-7 if index 10h bit 0 set, 0-15 if it
          is clear).

REG06 index 14h (R/W):  PLL Ref Div Fix
bit  0-4  N. Numerator. Guess 0 not valid. Used for f0-f15 if index 10h bit 0
          is clear.

REG06 index 15h W(R/W):  Sysclk Ref/VCO Div                       (Not RGB525)
bit  0-4  N. Numerator. Guess 0 not valid

REG06 index 16h (R/W):  Sysclk VCO Div                            (Not RGB525)
bit  0-5  M. Multiplier. 65-128, Stored as 0-63.
     6-7  DF. Divider. 0: /8, 1: /4, 2: /2, 1: /1. (Div=1,2,4,8).
Note: Memory Clock. The effective clock is: Ref*(M+65)/(N*Div), where Ref is
      the reference clock, typ 14.31828MHz and N the numerator from index 15h

REG06 index 20h-2Fh (R/W):  PLL Clock 0-15 (f0-f15)
bit  0-5  M. Multiplier. 65-128, Stored as 0-63.
     6-7  DF. Divider. 0: /8, 1: /4, 2: /2, 1: /1. (Div=1,2,4,8).
Note: Only active if index 10h bit 0 is clear. The effective clock is:
      Ref*(M+65)/(N*Div), where Ref is the reference clock, typ 14.31828MHz
      and N is the Numerator from index 14h.

REG06 index 20h-2Eh W(R/W):  PLL Clock 0-7 (m0/n0..)
bit  0-5  M. Multiplier. 65-128, Stored as 0-63.
     6-7  DF. Divider. 0: /8, 1: /4, 2: /2, 1: /1. (Div=1,2,4,8).
    8-12  N. Numerator. Guess 0 not valid
Note: Only active if index 10h bit 0 is set. The effective clock is:
      Ref*(M+65)/(N*Div), where Ref is the reference clock, typ 14.31828MHz

REG06 index 30h (R/W):  "Cursor Control"
bit  0-1  Cursor type. 0: Disabled, 2: Windows?, 3: X11 cursor
       2  Set for 64x64 cursor, clear for 32x32 cursor
       3
       5  Set for ??

REG06 index 31h W(R/W):  "Cursor X position"
bit  0-?  The horizontal position of the hardware cursor

REG06 index 33h W(R/W):  "Cursor Y position"
bit  0-?  The vertical position of the hardware cursor

REG06 index 35h (R/W):  Cursor Hot-Spot X

REG06 index 36h (R/W):  Cursor Hot-Spot Y

REG06 index 40h (R/W):  Cursor Color1 Red
bit  0-7  Red component of the Cursor Color1.

REG06 index 41h (R/W):  Cursor Color1 Green
bit  0-7  Green component of the Cursor Color1.

REG06 index 42h (R/W):  Cursor Color1 Blue
bit  0-7  Blue component of the Cursor Color1.

REG06 index 43h (R/W):  Cursor Color2 Red
bit  0-7  Red component of the Cursor Color2.

REG06 index 44h (R/W):  Cursor Color2 Green
bit  0-7  Green component of the Cursor Color2.

REG06 index 45h (R/W):  Cursor Color2 Blue
bit  0-7  Blue component of the Cursor Color2.

REG06 index 46h (R/W):  Cursor Color3 Red
bit  0-7  Red component of the Cursor Color3.

REG06 index 47h (R/W):  Cursor Color3 Green
bit  0-7  Green component of the Cursor Color3.

REG06 index 48h (R/W):  Cursor Color3 Blue
bit  0-7  Blue component of the Cursor Color3.

REG06 index 60h (R/W):  Border Color Red
bit  0-7  Red component of the Border Color.

REG06 index 61h (R/W):  Border Color Green
bit  0-7  Green component of the Border Color.

REG06 index 62h (R/W):  Border Color Blue
bit  0-7  Blue component of the Border Color.

REG06 index 70h (R/W):  Miscellaneous 1
bit    6

REG06 index 71h (R/W):  Miscellaneous 2
bit    0
       2  If set DACs & LUTs are 8bit wide, if clear only 6bits wide

REG06 index 72h (R/W):  Miscellaneous 3
REG06 index 73h (R/W):  Miscellaneous 4                           (Not RGB525)
REG06 index 82h (R/W):  DAC Sense
REG06 index 84h (R/W):  Misc Red
REG06 index 86h (R/W):  Misc Green
REG06 index 88h (R/W):  Misc Blue
REG06 index 8Eh (R/W):  PLL VCO Div In
REG06 index 8Fh (R/W):  PLL Ref Div In
REG06 index 90h (R/W):  VRAM Mask 0
REG06 index 91h (R/W):  VRAM Mask 1
REG06 index 92h (R/W):  VRAM Mask 2
REG06 index 93h (R/W):  VRAM Mask 3

REG06 index 100h-4FFh (R/W):  "Cursor Data"
Note: The cursor map is either a 64x64x2 (1024 bytes) or 32x32x2 (256bytes).
      The map data is stored with upper lines first, left pixels first. Each
      byte holds 4 pixels, with lowest pixel in bits 0-1 and highest on 6-7.
         High bit:  Low bit:    Resulting Screen data:
             0         0
             0         1
             1         0        Screen data
             1         1

REG07 (R/W):  Index Control
bit   0  If set the index at REG04 is autoincremented by each access of REG06




ICS 5301:
REG06 (R/W):  "Hidden DAC register"
bit 0-1  Power down if set ??
    2-4  Always 0
    5-7  Mode. 1,4,5: 15bit, 3,6: 16bit, 2,7: 24bit
Note: This register can be accessed by reading REG02 4 times, then the next
      read or write of REG02 will access this register. Any access of REG00,
      REG01 or REG03 will terminate the access to this register. The register
      can only be read or written once before the DAC is returned to normal
      mode (DAC type 4-1r1w).




IC Works W30c498, W30c516 Truecolor DACs:
REG06 (R/W):  Command Register
bit 0,2  (?) Clockmode for Mode 2 (2 8bit pixels/VCLK). 0: Clock < 22.5
            MHz, 1: Clock < 45 MHz, 2: Clock >= 45 MHz
      1  In palette modes this bit when set selects 8bit DACs, when clear 6bit
         DACs.
    4-7  Mode: 0: 8bit 1VCLK/pixel, 1: 15bit 1VCLK/pixel, 2: 8bit (2 pixels/
          VCLK), 3: 16bit 1VCLK/pixel, 5: 32bit 2VCLKs/pixel, 6: 16bit
          2VCLKs/pixel, 10: 15bit 2VCLKs/pixel
Note:  This register can also be accessed at REG02 by reading REG02 four times
       The fifth read will access of 3C6h will access this register. Only one
       read or write will be allowed (DAC type 4-1r1w3i), the 6th read returns
       84h, the 7th returns 98h and the 8th read returns 4Fh (at least for the
       w30c516).




MUSIC MU9c1880 and Diamond SS24 Truecolor DACs:
REG06 (R/W):  Command Register
bit 0,6  Red  Byte Position Shift. In 24bit mode delays the fetching of the
         first pixel of each scanline by 1 or 2 bytes to synchronize with the
         start of the first pixel.
           0: no delay, 1: delay 1 byte, 2: delay 2 bytes
  1-3,5  Selects the Hi- or Truecolor mode. 8: 15bit (5-5-5) HiColor,
           0Bh: 16bit (5-6-5) HiColor, 7: 24bit Truecolor (Red byte first).
      4  Pixel Mode Switch. In 15bit mode when this bit is set, the most
         significant bit of each 16bit pixel whether that pixel should be
         displayed as HiColor (bit 15=0) or Pseudo Color (bit 15=1).
         If this bit clear all pixels are displayed as HiColor
         This bit should be clear in 16bit mode and set in 24bit mode.
      7  If clear the DAC is in Pseudo Color mode, all other bits in this
         register are ignored, if set it is in a Hi- or Truecolor mode (15,16
         or 24 bits/pixel).
Note:  This register can also be accessed at REG02 by reading REG02 four times,
       The fifth read will return 8Eh (the ID for the MU9c1880/SS24) and then
       the next read or write of 3C6h will access this register. Only one read
       or write will be allowed (DAC type 5i-1r1w).




MUSIC MU9c4870 High Color(?) DAC
MUSIC MU9c4910 True Color DAC.
MUSIC MU9c9910 True Color DAC & Clock Generator.
REG04 (R/W):  PLL Write Index Register                             (9910 only)
bit 0-3  Selects the index register which will be accessed by the next write
         to REG05.

REG05 (R/W):  PLL Data Register                                    (9910 only)
The PLL registers accessed at this register are indexed via REG04 (writes) and
REG07 (reads). All (?) are two byte registers which are accessed via two reads
or writes (low byte first) each of the indexes have an internal flip-flop to
track low/high byte. Each read of REG05 will increment the read index (with
the flip-flop incremented first). Writes increment the write index (REG04)
similarly.

REG05 index 00h - 07h W(R/W):  f0-f7 PLL Parameters
bit  0-6  M. Numerator.
    8-11  N1. Quotient. Prescales REF for the PLL.
   12-13  N2. Clock divider. Divides the output clock by: 0: /1, 1: /2,
            2: /4, 3: /8
Resultant clock is: REF*(M+1)/((N1+1)*(2^N2)), where REF is the reference
clock, typically 14.31818MHz.

REG06 (R/W):  Command Register
bit   0  Powers down the DAC if set
    5-7  Mode. 5: 15bit, 6: 16bit, 7: 24bit
Note: This register can be accessed by reading REG02 3 times, then the fourth
      read will return the device ID and then the next read or write of REG02
      will access this register. Any access of REG00, REG01 or REG03 or writes
      to REG02 will terminate the access to this register, however reading of
      REG02 will not (DAC type 4i-1wNr).
      The MU9c9910 has ID 44h, the MU9c4910 has ID 82h, the MU9c4870 ??

REG07 (R/W):  PLL Read Index Register                              (9910 only)
bit 0-3  Selects the index register which will be accessed by the next read
         to REG05.




MUSIC MU9c9750 Low Power SYNDAC:
REG04 (R/W):  PLL Write Address Register
bit 0-3  Selects the index register which will be accessed by the next write
         to REG05.

REG05 (R/W):  PLL Parameters
The PLL registers accessed at this register are indexed via REG04 (writes) and
REG07 (reads). As all but index 0Eh are two byte registers which are accessed
via two reads or writes (low byte first) each of the indexes have an internal
flip-flop to track low/high byte. Each read of REG05 will increment the read
index (with the flip-flop incremented first). Writes increment the write
index (REG04) similarly.

REG05 index 00h - 07h W(R/W):  CLK0 f0-f7 PLL Parameters
bit  0-6  M. Numerator.
    8-11  N1. Quotient. Prescales REF for the PLL.
   12-13  N2. Clock divider. Divides the output clock by: 0: /1, 1: /2,
            2: /4, 3: /8
   14-15  PLL Mode Select. 0: Normal PLL mode - the output frequency is
          calculated as: f=REF*(M+1)/((N1+1)*(2^N2)), 1: High-resolution
          Low-frequency mode - same as PLL mode, but the output clock is
          divided by 1024, 2: OFF - The output is set HIGH, 3: Low-resolution
          Low-frequency mode - Output clock is: f=REF/((M+1)*(2^N2))
REF is the reference clock, typically 14.31818MHz. For best results the
following constraints should be observed: REF should be in the 5MHz - 32Mhz
range. REF/(N1+1) should be in the 2MHz - 16MHz range (for REF=14.31818MHz
 N1 should be in the range 1-6) and REF*(M+1)/(N1+1) should be in the 40MHz
 to 80MHz range.

REG05 index 08h W(R/W):  CLK0 fL0 PLL Parameters
Defines the CLK0 output when in LCD mode. Same format as index 0-7

REG05 index 09h W(R/W):  CLK0 fD0 PLL Parameters
Defines the CLK0 output when in Dormant mode. Same format as index 0-7

REG05 index 0Ah W(R/W):  CLK1 fA PLL Parameters
Defines the CLK1 output when in CRT mode and bit 4 of the PLL Control Register
 (index 0Eh) is clear. Same format as index 0-7

REG05 index 0Bh W(R/W):  CLK1 fB PLL Parameters
Defines the CLK1 output when in CRT mode and bit 4 of the PLL Control Register
 (index 0Eh) is set. Same format as index 0-7

REG05 index 0Ch W(R/W):  CLK1 fL1 PLL Parameters
Defines the CLK1 output when in LCD mode. Same format as index 0-7

REG05 index 0Dh W(R/W):  CLK1 fD1 PLL Parameters
Defines the CLK1 output when in Dormant mode. Same format as index 0-7

REG05 index 0Eh (R/W):  PLL Control Register
bit  0-2  CLK0 Select. Selects the CLK0 output in CRT mode (f0 - f7).
       4  CLK1 Select. Selects the CLK1 output in CRT mode. 0: fA, 1: fB
       5  CLK0 External Select Enable. If clear the CLK0 definition (f0-f7)
          is selected by the CS0-CS2 inputs, if set it is selected by bits
           0-2 of this register
       6  CLK0 Master Powerdown. If set the CLK0 PLL is powered down and the
          output is set HIGH.
       7  CLK1 Master Powerdown. If set the CLK1 PLL is powered down and the
          output is set HIGH.

REG06 (R/W):  Command Register
bit   0  LCD mode enable. If set the DAC goes into LCD mode where video flow
         through the DACs is stopped and the palette RAM is only accessed
         to service uP read/writes. The clocks CLK0,CLK1 are forced to the
         state defined in fL0/fL1 regardless of the state of the PLL Control
         register. The internal state of registers and palette RAM is
         maintained. See note
      6  Dormant Mode enable. If set the DAC goes into Dormant mode where
         the video flow though the DACs and the uP interface is stopped.
         The clocks CLK0,CLK1 are forced to the state defined in fD0/fD1
         regardless of the state of the PLL Control register. The internal
         state of registers and palette RAM is maintained. See note
Note: The CRT, LCD and Dormant modes are selected by a combination of the
      bits in this register and the PD0,PD1 input pins (x is don't care):
 PD1:  PD0:  Bit 6:  Bit 0:   Mode:  DAC:  RAM Access:   CLK0:    CLK1:
  1     0      0       0       CRT    On    Video&uP     f0-f7    fA,fB
  x     1      0       0       LCD    Off      uP         fL0      fL1
  1     0      0       1       LCD    Off      uP         fL0      fL1
  0     0      x       x     Dormant  Off     None        fD0      fD1
  x     x      1       x     Dormant  Off     None        fD0      fD1
Setting PD1=1 and PD0=0 allows full control from this register

REG07 (R/W):  PLL Read Address Register
bit  0-3  Selects the index register which will be accessed by the next read
          to REG05.




Oak OTI-66HC HiColor DAC:
REG06 (R/W):  "Hidden" Command Register
bit   0  If set the DAC powers down
    5-7  DAC mode. 5: 15bit, 6: 16bit
Note: This register can be accessed by reading REG02 4 times, then the next
      read or write of REG02 will access this register. Any access of REG00,
      REG01 or REG03 or writes to REG02 will terminate the access to this
      register, however reading of REG02 will not (DAC type 4-1wNr).




S3 86c708 (GenDac aka ICS5342) and 86c716 (SDAC aka ICS5300).

REG02 (R):  "Hidden DAC" register                                     (86c716)
Bit  4-7  7 for the 86c716.
Note: This is a special register overlaying the PEL register activated by an
      internal counter. Each access to 3C7h-3C9h resets the counter and each
      access to 3C6h increments it. When the counter reaches 4 this register
      is returned. The fifth read returns another register

REG04 (R/W):  PLL Write Register
bit  0-7  Controls the indexed register written at REG05. Each indexed
          register holds two bytes at the same index. Autoincremented after
          every two writes of REG05.

REG05 index 00h W(R/W):  f0 PLL M & N1/M2 divider
bit  0-6  M.  Quotient. Stored as 1-127, actual value 3-129
    8-12  N1. Frequency divider. Stored as 1-31, actual value 3-33
   13-15  N2. Divides the frequency. 0: /1, 1: /2, 2: /4, 3: /8
Note: Defines the frequency generate when clock 0 is selected
Note: See index 02h for details
      Possibly hardwired to 25.175MHz

REG05 index 01h W(R/W):  f1 PLL M & N1/M2 divider
bit  0-6  M.  Quotient. Stored as 1-127, actual value 3-129
    8-12  N1. Frequency divider. Stored as 1-31, actual value 3-33
   13-15  N2. Divides the frequency. 0: /1, 1: /2, 2: /4, 3: /8
Note: Defines the frequency generate when clock 1 is selected
Note: See index 02h for details
      Possibly hardwired to 28.322MHz

REG05 index 02h W(R/W):  f2 PLL M & N1/M2 divider
bit  0-6  M.  Quotient. Stored as 1-127, actual value 3-129
    8-12  N1. Frequency divider. Stored as 1-31, actual value 3-33
   13-15  N2. Divides the frequency. 0: /1, 1: /2, 2: /4, 3: /8
Note: Defines the frequency generate when clock 2 is selected
Note: Frequency is (M/N1)/(1 << N2) *base frequency.M and N1 are the actual
      values, not the stored ones. Typically the base frequency is 14.318 MHz.

REG05 index 03h W(R/W):  f3 PLL M & N1/M2 divider
bit  0-6  M.  Quotient. Stored as 1-127, actual value 3-129
    8-12  N1. Frequency divider. Stored as 1-31, actual value 3-33
   13-15  N2. Divides the frequency. 0: /1, 1: /2, 2: /4, 3: /8
Note: Defines the frequency generate when clock 3 is selected
Note: See index 02h for details

REG05 index 0Ah W(R/W):  Memory Clock
bit  0-6  M.  Quotient. Stored as 1-127, actual value 3-129
    8-12  N1. Frequency divider. Stored as 1-31, actual value 3-33
   13-15  N2. Divides the frequency. 0: /1, 1: /2, 2: /4, 3: /8
Note: Defines the frequency generate for the memory clock
Note: See index 02h for details

REG05 index 0Eh W(R/W):  PLL Control


REG06 (R/W):  Enhanced Command Register
bit 4-7  Mode: 0: Palette (1 pixel/VCLK), 1: Palette (2 pixels/VCLK), 2: 15bit
          (2 VCLKs/pixel), 3: 15bit (1 VCLK/pixel), 4: 24bit (3 VCLKs/pixel)
          - GenDAC only?, 5: 16bit (1 VCLK/pixel), 6: 16bit (2 VCLKs/pixel),
          7: 32bit (2 VCLKs/pixel), 0Eh: 24bit (3 VCLKs/pixel)

REG07 (R/W):  PLL Read Register
bit  0-7  Controls the indexed register read from REG05. Each indexed
          register holds two bytes at the same index. Autoincremented after
          every two reads of REG05.





SGS-Thompson STG1700/2/3 Truecolor DACs:
All the STG DACs have 16bit pixel data path, but the 1700 can not use the
packed 24bit mode where 2 pixels are transferred in 3 pixel clocks.
The 1703 has built-in clock generator.

REG04 (R/W):  Index Low
bit  0-7  Index for the register accessible via REG05. The high byte (always
           0) is in REG07.

REG05 (R/W):  Indexed Register
There are a series of indexed registers in the STG DACs. If REG06 bit 4 is set
they are accessed by the two index bytes to REG02 and then reading or writing
the indexed registers at REG02 (index will autoincrement). If REG06 bit 4 is
clear the index is written to REG04 & REG07 and the indexed register are read
or written at REG05.

REG05 index 00h (R):  Company ID
bit 0-7  44h for SGS-Thompson, 97h for ??

REG05 index 01h (R):  Device ID
bit 0-7  00h for STG1700, 02h for STG1702, 03h for STG1703

REG05 index 02h (R/W?):
bit 0-7  A1h ??

REG05 index 03h (R/W?):  Primary Pixel Mode
bit 0-7  Mode (this register only active if REG06 bit 3 set):
          2: 15bit 1VCLK per pixel
          3: 16bit 1VCLK per pixel
          4: 24bit 2VCLKs per pixel (2x 16bit -> 1x 24bit)
          5:  8bit 1/2 VCLKs per pixel (ie. 16bit -> 2x 8bit)
          9: (not 1700) 24bit 3/2 VCLKs per pixel (3x 16bit -> 2x 24bit)

REG05 index 04h (R/W?):  Secondary Pixel Mode
bit 0-7  same as index 3 ??

REG05 index 05h (R/W?):  PLL Control
bit 0-7  02h - for double clocking (16bit) ???

REG05 index 06h (R/W?):
bit 0-7  00h ??

REG05 index 07h (R/W?):
bit 0-7  88h ??

REG05 index 20h W(R/W):
bit  0-7  B. Quotient
    8-12  N1. Frequency divider.
   13-15  Divider (D). 0: /1, 1: /2, 2: /4, 3: /8
The effective clock is: Ref*D*(B+2)/(N1+2). Ref is the reference clock,
typically 14.31818MHz

REG06 (R/W):  Pixel Command Register
bit   0  Power down the DAC if set
      1  Set to get 8bit DACs in 256color mode, clear to get normal 6bit DACs
      2  Controls intensity ??
      3  If set the DAC is controlled by the indexed registers below.
      4  When set puts the dac into indexed mode, now write the index (2
         bytes) to this register, then each access to this register will read
         or write the particular indexed register and increment the index.
         This is the same index as in REG04/REG07.
    5-7  Selects the Hi/True color mode:  0: Standard (16/256color),
           5: 15bit(32K), 6: 16bit(64K), 7: 24bit(16m)
Note: This register can be accessed by reading REG02 4 times, then the next
      read or write of REG02 will access this register. Any access of REG00,
      REG01 or REG03 will terminate the access to this register, The register
      can only be read or written once per unlock sequence (DAC type 4-1w1r).

REG07 (R/W):  Index High
bit  0-?  High byte of the index in REG04. 0 for all current registers.



Sierra SC15021,25/6 Truecolor DACs:
The SC15021 supports 16bit pixel data path.

REG04 (R/W):  Overlay Write Address

REG05 (R/W):  Overlay Data

REG06 (R/W):  Command Register
bit 1-2  EXT mode select ?
      3  Gamma Correction enabled if set?
      4  If set 3C7h is the index port and 3C8h the data port for an extra
         register, also this register is then accessible directly at 3C6h.
  0,5-7  Mode:
           00h  Palette modes
           04h  32bit RGBx (red first) "double clocked" -  pixel data on both
                rising and falling edge of the dotclock
           05h  32bit BGRx (blue first) "double clocked"
           06h  24bit RGB/32bit RGBx (red first)
           07h  24bit BGR/32bit BGRx (blue first)
           08h  15bit (32K colors) "double clocked"
           09h  15bit (32K colors) "EXT" "double clocked"
           0Ah  15bit (32K colors)
           0Bh  15bit (32K colors) "EXT"
           0Ch  16bit (64K colors) "double clocked"
           0Eh  16bit (64K colors)
Note: This register can be accessed by reading REG02 4 times, then the next
      read or write of REG02 will access this register. Any access of REG00,
      REG01 or REG03 or writes to REG02 will terminate the access to this
      register, however reading of REG02 will not (DAC type 4-1wNr).

REG06 index 8 (R/W):  Auxiliary Control
bit    0  DAC and palette register width in palette modes.
          Set for 8bit and clear for 6 bit
       1  PED 75 IRE.
       2  Power Down.

REG06 index 9 (R):  ID1
bit  0-7  53h ('S')

REG06 index 0Ah (R):  ID2
bit  0-7  Version code. 0/36h/3Ah

REG06 index 0Bh (R):  ID3
bit  0-7  B1h for the SC15025/26, ACh for the SC15021

REG06 index 0Ch (R):  ID4
bit  0-7  41h

REG06 index 0Dh (R/W):  Pixel Mask Low
bit  0-7  ANDed with the pixel data, Low byte. Should normally be FFh.

REG06 index 0Eh (R/W):  Pixel Mask Middle
bit  0-7  ANDed with the pixel data, Middle byte. Should normally be FFh.

REG06 index 0Fh (R/W):  Pixel Mask High
bit  0-7  ANDed with the pixel data, High byte. Should normally be FFh.

REG06 index 10h (R/W):  Pixel Repack
bit    0  (15025/6) Set for 4x 8bit -> 1x 24bit, clear for 1x 8bit -> 8bit,
            2x 8bit -> 1x 16bit or 3x 8biot -> 1x 24bit
     0-3  (15021) Packaging: 2: 8bit -> 2x4bit, 4: 16bit -> 2x8bit,
             5: 3x16bit -> 2x24bit (2/3 clock), 6: 2x16bit -> 24bit (1/2
              clock), 8: 16bit -> 16bit (alternate?), 0: all others

REG06 index 11h (R/W):  Cursor                                         (15021)
bit  0-2  Cursor Delay. 0: None, 4: +1, 5: +2, 6: -1, 7: -2
     3-4  Cursor type. 0: disabled, 1: 3 colors, 2: 2 color MS-Windows style,
             3: 2 color X11 style
       7  Cursor Polarity

REG06 index 12h (R/W):  Secondary Control                              (15021)
bit  0-1  Mix control: 1: 8 -> 16 MixA or 8 -> 15 MixB, 2: 8 -> 16 MixB or
           8 -> 15 MixA, 0 for all others.

REG07 (R/W):  Overlay Read Address





Trident TKD8001 24bit DAC (also 9200CXr,9400CXi,9420DGi internal DAC):

REG06 (R/W):  Command Register
      0  (not 9200) Power down DAC if set ?
      1  (not 9400) In mode 0 this bit when set selects 8bit DACs, when clear
          6bit DACs. Should be set in 24bit mode, clear in 15/16 bit modes ?
    5-7  Mode:  0: Palette (16/256), 5: 15bit (32k), 7: 16bit (64k),
          6: 24bit (16m colors) bit 2 should be set in this mode
Note:  This register can also be accessed at REG02 by reading REG02 four
       times. Then the command register can be read or written at REG02.
       This access will be terminated by any access to REG00, REG01 or REG03
       or after a write to the command register (DAC type 4-Nr1w).




Trident 9440AGi internal 24bit DAC:

REG06 (R/W):  Command Register
      2  If set in the 15/16/24 bit modes pixels with the most significant
         bit set appears to be displayed as if in palette mode ?
    4-7  Mode:  1: 15bit (32k), 3: 16bit (64k), 0Dh: 24bit (16m colors)
         All other values appears to default to palette mode
Note:  This register can also be accessed at REG02 by reading REG02 four
       times. Then the command register can be read or written at REG02.
       This access will be terminated by any access to REG00, REG01 or REG03
       or after a write to the command register (DAC type 4-Nr1w).




TI TLC34058, Brooktree Bt458 DACs
These DACs are intended for high bandwidth systems and are not VGA compatible.
They use 4 or 5 separate pixel ports in parallel for higher bandwidth

REG04 (R/W)  Index Register.
bit  0-7  Index for accesses through 3C6h, 3C7h and 3C9h. For 3C7h and 3C9h
          there is also an internal counter for the (Red, Green and Blue)
          cycle. This counter is reset when this register is written.
          Each access to 3C7h or 3C9h will increment first the RGB counter and
          then this register.

REG05 (R/W)  Palette Data
bit  0-7  Palette data port. 3C8h selects the entry in the palette RAM. Each
          read or write of this register increments index, first through the
          Red, Green & Blue and then increments register 3C8h

REG06 (R/W)  Control Data.
bit  0-7  Data port for the Control registers. 3C8h is the index. Unlike 3C7h
          and 3C9h the index in 3C8h is not increased by reads and writes of
          this register

REG06 index 4 (R/W):  Read Mask Register
bit  0-7  The pixel data is ANDed with this byte before being passed to the
          palette RAM. This is similar to 3C6h in standard VGA systems.

REG06 index 5 (R/W):  Blink Mask Register
bit  0-7  In the blink off period the pixel data is ANDed with the inverse of
          this register, Ie. the '0' bits in this register will protect the
          corresponding bits of the pixel data from blinking, while '1' bits
          will force the corresponding pixel data bits low during the blink
          off period.

REG06 index 6 (R/W):  Command Register
bit    0  OL0 Display Enable. If clear the overlay pin 0 (OL0) is forced to 0
       1  OL1 Display Enable. If clear the overlay pin 1 (OL1) is forced to 0
       2  OL0 Blink Enable. If set (and bit 0 set) the overlay pin 0 toggles
          between 0 and the actual value at the blink rate
       3  OL1 Blink Enable. If set (and bit 1 set) the overlay pin 1 toggles
          between 0 and the actual value at the blink rate
     4-5  Blink Rate Select. Selects the blink rate in vertical periods:
            0: 16on/48off, 1: 16on/16off, 2: 32on/32off, 3: 64on/64off
       6  RAM Enable. If the overlay select pins (OL0-1) are 0 this bit
          selects the output. Set for palette RAM data, clear for overlay
          register 0.
       7  Multiplex Select. Set for 5:1 multiplexing, clear for 4:1
          multiplexing - pixel port E is ignored and should be tied low

REG06 index 7 (R/W):  Test Register
bit  0-3  Selects the data to be returned in bit 4-7 when reading this
          register. Selects upper or lower 4 bits of one of the 3 DAC inputs:
              1: return 4MSB of Red         9: return 4LSB of Red
              2: return 4MSB of Green      10: return 4LSB of Green
              4: return 4MSB of Blue       12: return 4LSB of Blue
     4-7  (R) Data selected by bits 0-3

REG07 (R/W)  Overlay Data
bit  0-7  Overlay data port. 3C8h selects the entry in the overlay RAM (0-3).
          Each read or write of this register increments index, first through
          the Red, Green & Blue and then increments register 3C8h




TI TLC34075, ATI68875 True color DACs
This DAC has an 8bit VGA port and a 32bit pixelport (P). The 32bit pixelport
P can be multiplexed for greater bandwidth. 6 or 8 bit DACs can be controlled
via the 8/6 pin (low=6bit, high=8bit).

REG08 (R/W):  General Control Register
bit    0  If set HSYNCOUT is active high, active low if clear
       1  If set VSYNCOUT is active high, active low if clear
       2  Enables split shift register transfer (VRAM) if set
       3  Enables special nibble mode if set
       4  Pedestal Enable Control. Set for a 7.5 IRE pedestal, clear for a 0
          IRE pedestal
       5  Sync Enable Control. If set enables sync on green.
       7  MUXOUT. If set the MUXOUT output pin is high, low if clear
Note: bits 2 and 3 can not both be set.

REG09 (R/W):  Input Clock Selection Register
bit  0-3  Selects the clock source (DOTCLK):
            0: CLK0, 1: CLK1, 2: CLK2, 3: CLK3 (TTL), 4: /CLK3 (TTL)
            8: CLK3 and /CLK3 are selected as an ECL clock source

REG0A (R/W):  Output Clock Selection Register
bit  0-2  Selects SCLK from DOTCLK.
            0: SCLK=DOTCLK, 1: SCLK=DOTCLK/2, 2: SCLK=DOTCLK/4
            3: SCLK=DOTCLK/8, 4: SCLK=DOTCLK/16, 5: SCLK=DOTCLK/32
            6,7: SCLK held at logic low
     3-5  Selects VCLK from DOTCLK.
            0: VCLK=DOTCLK, 1: VCLK=DOTCLK/2, 2: VCLK=DOTCLK/4
            3: VCLK=DOTCLK/8, 4: VCLK=DOTCLK/16, 5: VCLK=DOTCLK/32
            6,7: VCLK held at logic high

REG0B (R/W):  MUX Control Register
bit  0-5  Selects bits/pixel, pixel port and multiplexing:
            0Dh  24bpp from P. Red=P8-15, Green=P16-23, Blue=P24-31
            10h  1bpp. 4 pixels/DOTCLK from P0-3
            11h  1bpp. 8 pixels/DOTCLK from P0-7
            12h  1bpp. 16 pixels/DOTCLK from P0-15
            13h  1bpp. 32 pixels/DOTCLK from P0-31
            14h  2bpp. 2 pixels/DOTCLK from P0-3
            15h  2bpp. 4 pixels/DOTCLK from P0-7
            16h  2bpp. 8 pixels/DOTCLK from P0-15
            17h  2bpp. 16 pixels/DOTCLK from P0-31
            18h  4bpp. 1 pixel/DOTCLK from P0-3
            19h  4bpp. 2 pixels/DOTCLK from P0-7
            1Ah  4bpp. 4 pixels/DOTCLK from P0-15
            1Bh  4bpp. 8 pixels/DOTCLK from P0-31
            1Ch  8bpp. 1 pixels/DOTCLK from P0-7
            1Dh  8bpp. 2 pixels/DOTCLK from P0-15
            1Eh  8bpp. 4 pixels/DOTCLK from P0-31
            1Fh  4bpp. 4 pixels/DOTCLK from P0-31   (Special Nibble mode)
                 If the NFLAG input is low the 4 pixels are from P0-3, P8-11,
                 P16-19, P24-27 if high from P4-7, P12-15, P20-23, P28-31
            2Dh  8bpp from VGA port

REG0C (R/W):  Palette Page Register
bit  0-7  For 1,2 and 4 bits/pixel modes the upper bits of this register are
          used to select 1 of 128, 64 and 16 pages respectively in the
          palette RAM. The pixel data selects the entry within the page.

REG0E (R/W):  Test Register
bit  0-2  (W) Test mode. Selects the current test mode. Reading this register
              will step to the next test (see Next below).
              Val:  Next:    Description:
               0      1      Read Color Palette Red value
               1      2      Read Color Palette Green value
               2      0      Read Color Palette Blue value
               3      0      Read Identification code.
                             Returns 75h for 34075
               4      5      Read Ones Accumulation Red value
               5      6      Read Ones Accumulation Green value
               6      4      Read Ones Accumulation Blue value
               7      7      Analog Test. Result specified below.
       3  (R) Analog Test result. Set if the voltage selected by bit 6 (Green)
               or bit 7 (Red) is larger than the one selected by bit 4 (145mV
               reference) or bit 5 (Blue), clear if not.
       4  Select 145mV reference if set. Only applies to Analog test (bit 0-2
           = 7)
       5  Select Blue DAC if set. Only applies to Analog test (bit 0-2 = 7)
       6  Select Green DAC if set. Only applies to Analog test (bit 0-2 = 7)
       7  Select Red DAC if set. Only applies to Analog test (bit 0-2 = 7)

REG0F (W):  Reset State
Note: Writing to this register will cause a hardware reset of the DAC.




TI Viewpoint TVP3010,TVP3020,TVP3025,TVP3026 DACs
Note: The TVP3010, TVP3020 and TVP3025 use 3 address lines to select 8 direct
      registers (REG00-REG07) while the TVP3026 uses 4 lines to select 16
      direct registers (REG00-REG0F). The indexed registers (called REG06
      index XXh) are also handled differently

REG06 (R/W):  Index Register
bit  0-7  Index port to the indexed registers. First set this register, then
          read or write REG07
Note: On the TVP3026 the index is written to REG00 and data is read or written
      to/from REG0A

REG06 index 00h W(R/W):  Cursor X Position
bit 0-11  Horizontal position of the cursor

REG06 index 02h W(R/W):  Cursor Y Position
bit 0-11  Vertical position of the cursor

REG06 index 04h (R/W):  Sprite Origin X

REG06 index 05h (R/W):  Sprite Origin Y

REG06 index 06h (R/W):  Cursor Control
bit    4  X Window Mode if set
       6  Sprite Enable if set
       7  (3025) Planar Access. Set for Bt485 mode, clear for 3020 mode

REG06 index 08h W(R/W):  Cursor RAM Address
bit 0-15  Index into the cursor RAM on the DAC. Data is read or written at
          index 0Ah. Each access to index 0Ah will autoincrement this register

REG06 index 0Ah (R/W):  Cursor RAM Data
bit  0-7  Cursor data. Reading or writing this register will access the
          location in Cursor RAM specified in index 8 and will increment that
          index to allow consecutive reads or writes.
          The cursor is stored as a 64x64x2 bitmap with 4 2bit pixels per byte
          The two bits are interpreted as:
          High (odd)  Low (even)    ix 6 bit 4=1   ix 6 bit 4=0
            bit         bit          X11 mode        "normal"
             0           0         Transparent     Color 0
             0           1         Transparent     Color 1
             1           0           Color 0       Transparent
             1           1           Color 1       Inverse screen (XOR)
          Color 0 is the color in index 23h-25h, Color 1 is the color in index
           26h-28h

REG06 index 0Eh (R/W):  True Color Control                              (3025)
bit    0  8bit mode?. 0: 16/32bit, 1: 4/8bit
       1  Non-VGA mode. Set for non-VGA mode, clear for VGA mode
       2  BTmode. Set for Bt485 mode, clear for TI3020 mode

REG06 index 0Fh (R/W):  VGA Switch Control                              (3025)

REG06 index 10h W(R/W):  Window Start X

REG06 index 12h W(R/A):  Window Stop X

REG06 index 14h W(R/W):  Window Start Y

REG06 index 16h W(R/W):  Window Stop Y

REG06 index 18h (R/W):  MUX Control 1
bit  0-2  (3020) Direct Color mode.
            3: Selects 6-6-4 16bit mode (6red-6green-4blue).
            4: Selects 5-5-5 15bit mode (5red-5green-5blue).
            5: Selects 5-6-5 16bit mode (5red-6green-5blue).
            6: Selects 8-8-8 24bit mode (8red-8green-8blue).
     0-3  (3025) Direct Color mode
             0Ch: Selects 5-5-5 mode (5red-5green-5blue).
             0Dh: Selects 5-6-5 mode (5red-6green-5blue).
             0Eh: Selects 8-8-8 mode (8red-8green-8blue).
       6  (3025) D/T mode. 0: Selects "D" mode, 1: selects "T" mode.
       7  Pseudo Color, set for palette modes

REG06 index 19h (R/W):  MUX Control 2


REG06 index 1Ah (R/W):  Input Clock Select
bit    0  (3020) If set selects ICLK1, if clear ICLK0
     0-2  (3025) Selects the input clock.
            0: ICLK0, 1: ICLK2, 2: ICLK2, 3: ICLK2_I ?, 4: ICLK2_E ?
            5: PLL as input clock.
       4  If set doubles the selected input clock.

REG06 index 1Bh (R/W):  Output Clock Select
bit  0-1  Multiplex. 0: (R1), 1: 1:2 Mux (1x64 -> 2x 24/32bit) R2, 2: 1:4 Mux
           (1x64 -> 4x 15/16bit) R4, 3: 1:8 Mux (1x64 -> 8x 8bit) R8
     3-4  Clock range. 0: <=60MHz (V1), 1: >60MHz & <=120MHz (V2), 2: >120MHz
           (V4), 3: V8
       6  S ?
       7  (3025) NS ?
Note: Set to 3Eh in VGA passthrough mode

REG06 index 1Ch (R/W):  Palette Page

REG06 index 1Dh (R/W):  General Control
bit    0  Vertical Sync Polarity. 0: Negative, 1: Positive
       1  Horizontal Sync Polarity. 0: Negative, 1: Positive
       5  Sync on Green if set

REG06 index 1Eh (R/W):  Misc Control                                    (3025)
bit    0  Powerdown
       1  Dotclock disable
       2  Internal 6/8 Control. If set selection of 6 or 8 bits DAC mode in
          palette modes is done by bit 3, if clear from the 6/8 input pin.
       3  8Bpp. If set selects 8bit DAC and palette registers in palette
          modes, if clear selects 6bit DAC & registers.
          This bit only active if bit 2 is set.
       5  VCLK Polarity.
       6  LCLK Latch. 0: VCLK
       7  Loop PLL RCLK.

REG06 index 20h (R/W):  Overscan Color Red

REG06 index 21h (R/W):  Overscan Color Green

REG06 index 22h (R/W):  Overscan Color Blue

REG06 index 23h (R/W):  Cursor Color 0 Red
bit  0-7  The red component of the cursor background color.

REG06 index 24h (R/W):  Cursor Color 0 Green
bit  0-7  The green component of the cursor background color.

REG06 index 25h (R/W):  Cursor Color 0 Blue
bit  0-7  The blue component of the cursor background color.

REG06 index 26h (R/W):  Cursor Color 1 Red
bit  0-7  The red component of the cursor foreground color.

REG06 index 27h (R/W):  Cursor Color 1 Green
bit  0-7  The green component of the cursor foreground color.

REG06 index 28h (R/W):  Cursor Color 1 Blue
bit  0-7  The blue component of the cursor foreground color.

REG06 index 29h (R/W):  Auxillary Control
bit    0  Window Complement if set
       3  (3020) Self Clock mode if set

REG06 index 2Ah (R/W):  General IO Control
bit  0-4

REG06 index 2Bh (R/W):  General IO Data

REG06 index 2Ch (R/W):  PLL Control                                     (3025)
bit  0-1  Write 0 to reset the internal counter for the PLL data registers
          Each write to index 2Dh/2Eh/2Fh will increment this field.

REG06 index 2Dh (R/W):  Pixel Clock PLL Data                            (3025)
bit  0-?  N. Divider (3-28). Stored as 1-26. Could probably be larger ??
    8-14  M. Divident (3-129). Stored as 1-127
   16-17  P. Clock multiplier. 0: *8, 1: *3, 2: *2, 3: *1
      19  PLL Enable. Enables the PLL clock if set
Note: This register consists of 3 bytes at the same index. Writing 00h to
      index 2Ch resets the internal counter so that the next access to this
      index accesses the first byte. Each access autoincrements the internal
      counter. The clock is calculated as: Ref * P * (M+2)/(N+2)

REG06 index 2Eh (R/W):  MCLK PLL Data                                   (3025)
bit  0-?  N. Divider (3-28). Stored as 1-26. Could probably be larger ??
    8-14  M. Divident (3-129). Stored as 1-127
   16-17  P. Clock multiplier. 0: *8, 1: *3, 2: *2, 3: *1
      19  PLL Enable. Enables the PLL clock if set
      23  Set when writing new PLL data ?

REG06 index 2Fh (R/W):  Loop Clock PLL Data                             (3025)
bit  0-?  N. Divider (3-28). Stored as 1-26. Could probably be larger ??
    8-14  M. Divident (3-129). Stored as 1-127
   16-17  P. Clock multiplier. 0: *8, 1: *3, 2: *2, 3: *1
      19  PLL Enable. Enables the PLL clock if set

REG06 index 30h W(R/W):  Color Key OLVGA

REG06 index 32h W(R/W):  Color Key Red

REG06 index 34h W(R/W):  Color Key Green

REG06 index 36h W(R/W):  Color Key Blue

REG06 index 38h (R/W):  Color Key Control

REG06 index 39h (R/W):  MCLK/DCLK Control                               (3025)

REG06 index 3Ah (R/W):  Sense Test

REG06 index 3Bh (R/W):  Test Data

REG06 index 3Ch W(R/W):  CRC

REG06 index 3Eh (R/W):  CRC Control

REG06 index 3Fh (R):  ID
bit  0-7  Chip ID. 20h for TVP3020, 25h for TVP3025, 26h for TVP3026
          Guess: 10h for TVP3010

REG06 index D5h (R/W):  Mode 85 Control                                 (3025)

REG0A (R/W): Data Register (3025)


UMC UM70c178 Hi-Color DACs:

REG06 (R/W):  Command Register
bit 0-4  (R) Always 0
    5-7  Mode: 5: 15bit, 7: 16bit.
Note:  This register can also be accessed at REG02 by reading REG02 four
       times. Then the command register can be read or written at REG02.
       This access will be terminated by any access to REG00, REG01 or REG03
       or after write of the command register.  (DAC type 4-Nr1w).




UMC UM70c188 TrueColor DACs:

REG06 (R/W):  Command Register
bit 0-3  (R) Always 0
      4  Set in 24bit mode, clear in all other modes
    5-7  Mode: 5: 15bit, 7: 16bit. Don't care for 24bit
Note:  This register can also be accessed at REG02 by reading REG02 four
       times. Then the command register can be read or written at REG02.
       This access will be terminated by any access to REG00, REG01 or REG03
       or after a read or write of the command register.  (DAC type 4-1r1w).





Forcing HiColor DACs into command mode:
Note: This works on the Sierra, ATT, Winbond DACs and clones, not on the
 Brooktree or TI DACs, also the MUSIC DACs will require an extra read of 3C6h.

procedure dactocomm;   {switches DAC to command register}
var x:word;
begin
  x:=inp($3C8);    {clear old state}
  x:=inp($3C6);
  x:=inp($3C6);
  x:=inp($3C6);    {Read $3C6 4 times.}
  x:=inp($3C6);
end;

Now reads and writes to $3C6 will access the command register. Depending on
the DAC type you may have multiple read/writes, one write/multiple reads or
one read/write of the command register before it switches back to the PEL
register. Any access to $3C7-$3C9 will switch back to the PEL mask register.


Forcing HiColor DACs into normal mode:

procedure dactopel;  {switches DAC back to normal mode}
var x:word;
begin
  x:=inp($3C8);
end;



function testdac:string;
var
  x,y,z,v,oldcommreg,oldpelreg:word;

type
  pel=record
        index,red,green,blue:byte;
      end;

procedure readpelreg(index:word;var p:pel);
begin
  p.index:=index;
  disable;
  outp($3C7,index);
  p.red  :=inp($3C9);
  p.blue :=inp($3C9);
  p.green:=inp($3C9);
  enable;
end;

procedure writepelreg(var p:pel);
begin
  disable;
  outp($3C8,p.index);
  outp($3C9,p.red);
  outp($3C9,p.blue);
  outp($3C9,p.green);
  enable;
end;

function setcomm(cmd:word):word;
begin
  dac2comm;
  outp($3c6,cmd);
  dac2comm;
  setcomm:=inp($3c6);
end;

procedure waitforretrace;
begin
  repeat until (inp(CRTC+6) and 8)=0;
  repeat until (inp(CRTC+6) and 8)>0;    {Wait until we're in retrace}
end;

function dacis8bit:boolean;
var
  pel2,x,v:word;
  pel1:pel;
begin
  pel2:=inp($3C8);
  readpelreg(255,pel1);
  v:=pel1.red;
  pel1.red:=255;
  writepelreg(pel1);
  readpelreg(255,pel1);
  x:=pel1.red;
  pel1.red:=v;
  writepelreg(pel1);
  outp($3C8,pel2);
  dacis8bit:=(x=255);
end;

function testdacbit(bit:word):boolean;
begin
  dac2pel;
  outp($3C6,oldpel and (bit xor $FF));
  dac2comm;
  disable;
  outp($3C6,oldcomm or bit);
  v:=inp($3C6);
  outp($3C6,v and (bit xor $FF));
  enable;
  testdacbit:=(v and bit)<>0;
end;

begin

  setDAC(_dac8,'Normal');
  dac2comm;
  oldcomm:=inp($3C6);
  dactopel;
  oldpel:=inp($3c6);

  dac2comm;
  outp($3c6,0);
  dac8:=dacis8bit;
  dac2pel;

  notcomm:=oldcomm xor 255;
  outp($3c6,notcomm);
  dac2comm;
  v:=inp($3c6);
  if v<>notcomm then
    if (setcomm($E0) and $e0)<>$e0 then
    begin           {Bits 5-7 of command register NOT writable.}
      dac2pel;
      x:=inp($3C6);
      repeat
        y:=x;         {wait for the same value twice}
        x:=inp($3C6);
      until (x=y);
      z:=x;
      dac2comm;
      if daccomm<>$8E then
      begin                 {If command register=$8e, we've got an SS24}
        y:=8;
        repeat
          x:=inp($3C6);
          dec(y);
        until (x=$8E) or (y=0);
      end
      else x:=daccomm;
      if x=$8e then setDAC(_dacss24,'SS24')
               else setDAC(_dac15,'Sierra SC11486');
      dac2pel;
    end
    else begin
      if (setcomm($60) and $E0)=0 then
      begin
        if (setcomm(2) and 2)>0 then setDAC(_dacatt,'ATT 20c490')
                                else setDAC(_dacatt,'ATT 20c490');
      end
      else begin
        x:=setcomm(oldcomm);
        if inp($3c6)=notcomm then
        begin
          if setcomm($FF)<>$ff then setDAC(_dacadac1,'Acumos ADAC1')
          else begin
            dac8now:=dacis8bit;
            dac2comm;
            outp($3C6,(oldcomm or 2) and $FE);
            dac8now:=dacis8bit;
            if dac8now then
              if dacis8bit then setDAC(_dacatt,'ATT 20c491')
                           else setDAC(_dacCL24,'Cirrus 24bit DAC')
            else setDAC(_dacatt,'ATT 20c492');
          end;
        end
        else begin
          if trigdac=notcomm then setDAC(_dacCL24,'Cirrus 24bit DAC')
          else begin
            dac2pel;
            outp($3c6,$FF);
            case trigdac of
              $44:setDAC(_dacmus,'MUSIC ??');
              $82:setDAC(_dacmus,'MUSIC MU9C4910');
              $8e:setDAC(_dacss24,'Diamond SS2410');
            else
              if testdacbit($10) then setDAC(_dacsc24,'Sierra 16m')
              else if testdacbit(4) then setDAC(_dacUnk9,'Unknown DAC #9')
                                else setDAC(_dac16,'Sierra 32k/64k');
            end;
          end;
        end;
      end;
    end;

    dac2comm;
    outp($3c6,oldcomm);
  end;
  dac2pel;
  outp($3c6,oldpel);

  if (dactype=_dac8) and (DAC_RS2<>0) and (DAC_RS3<>0) then
  begin
    oldpel :=inp($3C6);
    oldcomm:=inp($3C6+DAC_RS2);
    outp($3C6+DAC_RS2,oldpel xor $FF);
    if (inp($3C6)=oldpel) and (inp($3C6+DAC_RS2)=(oldpel xor $FF)) then
      SetDAC(_dacBt484,'Brooktree Bt484');

    outp($3C6+DAC_RS2,oldcomm);
    outp($3C6,oldpel);
  end;



  if dactype=_dac8 then
  begin
    WaitforRetrace;
    outp($3C8,222);
    outp($3C9,$43);
    outp($3C9,$45);
    outp($3C9,$47);    {Write 'CEGEDSUN' + mode to DAC index 222}
    outp($3C8,222);
    outp($3C9,$45);
    outp($3C9,$44);
    outp($3C9,$53);
    outp($3C8,222);
    outp($3C9,$55);
    outp($3C9,$4E);
    outp($3C9,13);     {Should be in CEG mode now}
    outp($3C6,255);
    x:=(inp($3c6) shr 4) and 7;
    if x<7 then
    begin
      setDAC(_dacCEG,'Edsun CEG rev. '+chr(x+48));
      WaitforRetrace;
      outp($3C8,223);
      outp($3C9,0);    {Back in normal dac mode}
    end;
  end;
end;


This ID's all known DAC types, except:
 - Sierra "mark2" and "Mark3" are all ID'd as Mark 3.

 - Avance Logic ALG1101 DAC can not be ID'd.

 - TI 34075, ATI 68830, 68860 and 68875 can not be ID'd

 - The Edsun CEG test has not been verified.