Appendix D. General CRT Controller Registers

This information is provided in the event the programmer requires more complex control of the video hardware. Use of this information is strictly at your own risk, as some manufacturers use the entries below for contrasting purposes.

Group Resister Index Port Data Port Index Value
CRT Control Horizontal Total 3D4h 3D5h 00h
Horz. Display End 01h
Start Horz. Blanking 02h
End Horz. Blanking 03h
Start Horz. Retrace 04h
End Horz. Retrace 05h
Vertical Total 06h
Overflow 07h
Preset Scan Row 08h
Max Scan Line 09h
Cursor Start 0AH
Cursor End 0Bh
Start Addr. High 0Ch
Start Addr. Low 0Dh
Cursor Location High 0Eh
Cursor Location Low 0Fh
Start Vert. Retrace 10h
End Vert. Retrace 11h
End Vert. Display 12h
Offset 13h
Underline Location 14H
Start Vert. Blanking 15h
End Vert. Blanking 16h
Mode Control 17h
Line Compare 18h
Sequencer Reset 3C4H 3C5H 00h
Clocking Mode 01h
Map Mask 02h
Character Map Select 03h
Graphics Set/Reset 3CEH 3CFH 00h
Set/Reset Enable 01h
Color Compare 02h
Data Rotate 03h
Read map Select 04h
Mode 05h
Miscellaneous 06h
Color Don't Care 07h
Bit Mask 08h
Attribute Palette 3C0H 3C0H 00h - 0Fh
Mode Control 10h
Overscan Color 11h
Color Plane Enable 12h
Horz. Pixel Panning 13h
Color Select 14h
General Misc. Output 3CCH 3C2H R/W
Feature Control 3CAH 3DAH R/W
Status #0 3C2H read only
Status #1 3DAh read only
Color Color Address Write 3C8H write only
Color Address Read 3C7H write only
Color Data Register 3C9H 3C9H R/W

Notes:

1. Registers specified as Read, Write or R/W use addresses listed without indexes. First address is read location, second write.

2. Bit 7 on End Vert. Retrace is write protect for CRT registers at indexes 0 to 7.

3. Bit 4 on Overflow is Line Compare bit 8.

4. Bit 6 on Max. Scanline is Line Compare bit 9.

5. Bit 3 on Status #1 is Vertical Retrace.

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