Copyright(C) 1994,1995,1996,1997 Terumasa KODAKA , Takeshi KONO
â– Video Board
Applicable to PC-9801-72, PC-98GS-02
Explanation o The video board (PC-9801-72) and video board GS (PC-98GS-02) are
expansion boards for synthesizing and displaying video signals on a computer
screen at any size.
NTSC composite video signals and S-video signals can be input, allowing video
images to be captured and processed.
Note that the PC-9801-72 is also included in the PC-9801-76 (multimedia engine set).
o The I/O addresses used by the video board are as follows.
------------+-------+-----+--------------------------------------------------
I/O address | width | R/W | contents
------------+-------+-----+--------------------------------------------------
AF67h | BYTE | R/W | Video board control [INDEX]
AF6Ah | WORD | R/W | Video board control [DATA]
------------+-------+-----+--------------------------------------------------
I/O AF67h
Name Video board control [INDEX]
Undocumented
Chip
Function
[READ/WRITE]
bit 7-0: Register address setting
Explanation o Specifies the register number of the video board
Related I/O AF6Ah
I/O AF6Ah
Name Video board control [DATA]
Undocumented
Chip
Function
[READ/WRITE]
bit 15-0: Data input/output
----------------+--------------------------------------
Register number | contents
----------------+--------------------------------------
08h | Transparent color setting
| bit 15-6: Unknown
| bit 5: Transparent color specification
| 1 = Specify transparent color
| 0 = Specify transparent
| bit 4: Blending mode
| 1 = Semi-transparent blending
| 0 = Transparent blending (normal)
| bit 3-0: Unknown
----------------+--------------------------------------
09h | Blue upper limit level
| bit 15-8: Unused (set to 0)
| bit 7-0: Blue upper limit level
----------------+--------------------------------------
0Ah | Red upper limit level
| bit 15-8: Unused (set to 0)
| bit 7-0: Red upper limit level
----------------+--------------------------------------
0Bh | Green upper limit level
| bit 15-8: Unused (set to 0)
| bit 7-0: Green upper limit level
----------------+--------------------------------------
0Ch | Transparent color range specification
| bit 15-3: Unused
| bit 2: Green transparent range
| bit 1: Red transparent range
| bit 0: Blue transparent range
| 1 = Inside the upper and lower limits is transparent
| 0 = Outside the upper and lower limits is transparent
----------------+--------------------------------------
0Dh | Blue lower limit level
| bit 15-8: Unused (set to 0)
| bit 7-0: Blue lower limit level
----------------+--------------------------------------
0Eh | Red lower limit level
| bit 15-8: Unused (set to 0)
| bit 7-0: Red lower limit level
----------------+--------------------------------------
0Fh | Green lower limit level
| bit 15-8: Unused (set to 0)
| bit 7-0: Green lower limit level
----------------+--------------------------------------
10h | Specify chrominance range
| * Details unknown
----------------+--------------------------------------
11h | Lower limit of luminance range
| bit 15-8: Unused (set to 0)
| bit 7-0: Lower limit of luminance range
----------------+--------------------------------------
12h | Specify chrominance range
| * Details unknown
----------------+--------------------------------------
13h | Upper limit of luminance range
| bit 15-8: Unused (set to 0)
| bit 7-0: Upper limit of luminance range
----------------+--------------------------------------
14h | Effect on video screen
| bit 15-9: Unused (set to 0)
| bit 8: Contour image quality correction of video screen
| 1 = Set
| 0 = Do not set
| bit 7,6: Unused (set to 00b)
| bit 5,4: Video effect
| 00b = No video effect
| 01b = Make the specified range monochrome
| 11b = Make the specified range transparent
| bit 3: Specify the luminance range direction
| bit 2: Specify the chrominance range direction
| 1 = Inside
| 0 = Outside
| bit 1: Control the luminance range
| bit 0: Control the chrominance range
| 1 = Enabled
| 0 = Disabled
----------------+--------------------------------------
16h | Brightness/illuminance adjustment
| bit 15-8: Adjust the brightness (brightness)
| * Signed 8 bits
| bit 7-0: Adjust the illuminance (contrast)
| * Signed 8 bits
----------------+--------------------------------------
17h | Saturation/intensity adjustment
| bit 15-8: Adjust the saturation (hue)
| * Signed 8 bits
| bit 7-0: Adjust the intensity (darkness)
| * Signed 8 bits
----------------+--------------------------------------
18-1Ah,1Eh | Reduced size setting?
| * Details unknown
----------------+--------------------------------------
1Fh | Display horizontal coordinate (display coordinate)
----------------+--------------------------------------
20h | Display vertical coordinate (display coordinate)
----------------+--------------------------------------
21h | Display horizontal size (video virtual coordinate)
----------------+--------------------------------------
22h | Display vertical size (video virtual coordinate)
----------------+--------------------------------------
23h | Display start horizontal coordinate
----------------+--------------------------------------
24h | Display start vertical coordinate
----------------+--------------------------------------
26h | Field mode
| bit 15-1: Unknown
| bit 0: Field mode specification
| 1 = 2 field mode
| 0 = 1 field mode
----------------+--------------------------------------
28h | Frame buffer read control
| bit 15-8: Unused
| bit 7: Unused
| bit 6: Green plane read flag
| bit 5: Red plane read flag
| bit 4: Blue plane read flag
| 1 = Read
| 0 = Do not read
| bit 3: Unused
| bit 2: Fast erase flag
| * Automatically reset
| bit 1: Read start flag?
| bit 0: Still mode setting
----------------+--------------------------------------
29h | Read start horizontal coordinate (video virtual coordinate)
----------------+--------------------------------------
2Ah | Read start vertical coordinate (video virtual coordinate)
----------------+--------------------------------------
2Bh | Read end horizontal coordinate (video virtual coordinate)
----------------+--------------------------------------
2Ch | Read end vertical coordinate (video virtual coordinate)
----------------+--------------------------------------
2Dh | Blue plane read data
----------------+--------------------------------------
2Eh | Red plane read data
----------------+--------------------------------------
2Fh | Green plane read data
----------------+--------------------------------------
30h | Write control
| bit 15-8: Unused
| bit 7: Unused
| bit 6: Green plane write flag
| bit 5: Red plane write flag
| bit 4: Blue plane write flag
| 1 = Write
| 0 = Do not write
| bit 3,2: Unused
| bit 1: Read start flag?
| bit 0: Frame buffer mode
----------------+--------------------------------------
31h | Write start horizontal coordinate (video virtual coordinate)
----------------+--------------------------------------
32h | Write start vertical coordinate (video virtual coordinate)
----------------+--------------------------------------
33h | Write end horizontal coordinate (video virtual coordinate)
----------------+--------------------------------------
34h | Write end vertical coordinate (video virtual coordinate)
----------------+--------------------------------------
35h | Blue plane write data
----------------+--------------------------------------
36h | Red plane write data
----------------+--------------------------------------
37h | Green plane write data
----------------+--------------------------------------
38-43h,4Dh | Reduced size setting?
| * Details unknown
----------------+--------------------------------------
FFh | Video board presence ID
| 0000h=Video board presence ID
| * Read only
----------------+--------------------------------------
Explanation o Reads and writes the register of the video board specified by I/O AF67h.
Related I/O AF67h