CD Actual 1

home *** CD-ROM | disk | FTP | other *** search

/ CD Actual 1 / PC Actual CD 01.iso / share / dos / progr / vga.doc / text0000.txt < prev

Wrap

Text File | 1993-02-19 | 23.4 KB | 518 lines

OK...here it comes.... Documentation over the I/O registers for standard VGA-cards Documentated by Shaggy of The Yellow One. Email: D91-SJD@TEKN.HJ.SE Feel free to spread this to who ever wants it..... ------------------------------------------------------------ Port-Index: - Port: Write/03c2h Read/03cch usage: d7 Vertical sync polarity d6 Horizontal sunc polarity d5 Odd /even page d4 Disable video d3 Clock select 1 d2 Clock select 0 d1 Enable/Disable display RAM d0 I/O address select Description: Sync polarity: Bits are set as below for VGA displays that use sync polarity to determine screen resolution. Many newer multiple frequency displays are insensitive to sync polarity d7 d6 Resolution 0 0 Invalid 0 1 400 lines 1 0 350 lines 1 1 480 lines I/o address select: When set to zero, selects the monochrome I/O address space (3bx). When set to one, it selects the color I/O address space (3dx) ------------------------------------------------------------ Port-Index: - Port: 03c2h ; read only usage: d7 Vertical Retrace Interrupt pendling d6 Feature connector bit 1 d5 Feature connector bit 0 d4 Switch sense d0-d3 Unused Description: d7 uses IRQ2 ------------------------------------------------------------ Port-Index: - Port: 03bah,03dah ; read only usage: d3 Vertical retrace d0 Horizontal retrace ------------------------------------------------------------ Port-Index: - Port: 03c3h,46e8h usage: d7-d1 Reserved d0 VGA enable/disable (03c3h only) Description: Disables access to display memmory and the other VGA's ports ------------------------------------------------------------ Port-Index: 00h Port: 03d4h, 03b4h usage: Horizontal total Description: Total number of characters in horizontal scan minus five ( including blanked and border characters) ------------------------------------------------------------ Port-Index: 01h Port: 03d4h, 03b4h usage: Horizontal display enable Description: Total number of characters displayed in horizontal scan minus one. ------------------------------------------------------------ Port-Index: 02h Port: 03d4h, 03b4h usage: Start horizontal blanking Description: Character at which blanking starts ------------------------------------------------------------ Port-Index: 03h Port: 03d4h, 03b4h usage: End horizontal blanking d7 Test d6 Skew control d5 Skew control d0-d4 End blanking Description: End blanking: is five LSB bits of six-bit value, which define the character at which blanking stops. The MSB bit of this value is in register index 5. ------------------------------------------------------------ Port-Index: 04h Port: 03d4h, 03b4h usage: Start horizontal retrace Description: Character at which horizontal retrace starts ------------------------------------------------------------ Port-Index: 05h Port: 03d4h, 03b4h usage: End horizontal retrace d7 End horizontal blanking bit 5 d6 Horizontal retrace delay d5 Horizontal retrace delay d0-d4 End horizontal retrace Description: End horizontal retrace: defines the character at which horizontal retrace ends ------------------------------------------------------------ Port-Index: 06h Port: 03d4h, 03b4h usage: Vertical total Description: Total number of horizontal scan lines minus two (including blanked and border characters). MSB bits of this value are in register index 7 ------------------------------------------------------------ Port-Index: 07h Port: 03d4h, 03b4h usage: Overflow register d7 Vertical retrace start (bit 9) d6 Vertical display enable end (bit 9) d5 Vertical total (bit 9) d4 Line compare (bit 8) d3 Start vertical blank (bit 8) d2 Vertical retrace start (bit 8) d1 Vertical display enable end (bit 8) d0 Vertical total (bit 8) ------------------------------------------------------------ Port-Index: 08h Port: 03d4h, 03b4h usage: Preset row scan d7 Unused d6 Byte panning control d5 Byte panning control d0-d4 Preset row scan Description: Byte panning control: is used to control byte panning. This register together with attribute controller register 13h allows for up to 31 pixels of panning in double word modes Preset row scan: Which character scan line is the first to be displayed ------------------------------------------------------------ Port-Index: 09h Port: 03d4h, 03b4h usage: Maximum scan line/Character height d7 double scan d6 bit d9 of line compare register d5 bit d9 of start vertical blank register d0-d4 Maximum scan line Description: d0-d5=Character height-1, only in textmodes ------------------------------------------------------------ Port-Index: 0ah Port: 03d4h, 03b4h usage: Cursor start d7,d6 Reserved (0) d5 Cursor off d4-d0 Cursor start Description: ------------------------------------------------------------ Port-Index: 0bh Port: 03d4h, 03b4h usage: Cursor end d7 reserved d6,d5 Cursor skew d4-d0 Cursor end Description: ------------------------------------------------------------ Port-Index: 0ch Port: 03d4h, 03b4h usage: Start address high ------------------------------------------------------------ Port-Index: 0dh Port: 03d4h, 03b4h usage: Start address low Description: Determine the offset in display memory to be displayed on the upper-left corner on the screen ------------------------------------------------------------ Port-Index: 0eh Port: 03d4h, 03b4h usage: Cursor location (high byte) ------------------------------------------------------------ Port-Index: 0fh Port: 03d4h, 03b4h usage: Cursor location (low byte) Description: Where the cursor is displayed on screen ------------------------------------------------------------ Port-Index: 10h Port: 03d4h, 03b4h usage: Vertical retrace start Description: 8 bits out of 10 ------------------------------------------------------------ Port-Index: 11h Port: 03d4h, 03b4h usage: Vertical retrace end d7 Write protect CRTC register 0 to 7 d6 refresh cycle select d5 enable vertical interrupt (when 0) d4 Clear vertical interrupt (when 0) d0-d3 Vertical retrace end ------------------------------------------------------------ Port-Index: 12h Port: 03d4h, 03b4h usage: Vertical display enable end Description: eight LSB bits out of ten-bit value which define scan line minus one at which the display ends. The other two are in CRTC register index 7 ------------------------------------------------------------ Port-Index: 13h Port: 03d4h, 03b4h usage: Offset / Logical screen width Description: Logical screen width between successive scan lines ------------------------------------------------------------ Port-Index: 14h Port: 03d4h, 03b4h usage: Underline location register d7 Reserved d6 Double word mode d5 count by 4 d0-d4 Underline location Description: Underline location: Monochrome textmode only ------------------------------------------------------------ Port-Index: 15h Port: 03d4h, 03b4h usage: Start vertical blanking Description: eight LSB bits of ten-bit value minus one which define at which scan line the vertical blanking starts. The other two bits are in CRTC registers index 7 and 9 ------------------------------------------------------------ Port-Index: 16h Port: 03d4h, 03b4h usage: End vertical blanking Description: eight LSB bits of a value which determine the scan line after which vertical blanking ends. ------------------------------------------------------------ Port-Index: 17h Port: 03d4h, 03b4h usage: Mode control register d7 Enable vertical and hoizontal retrace d6 Byte mode (1), word mode (0) d5 Address wrap d4 Reserved d3 count by 2 d2 multiple vertical by 2 (use half in CRTC (8,10,12,14,18) d1 Select row scan counter (not used) d0 compatibilty mode support (enable interleave) ------------------------------------------------------------ Port-Index: 18h Port: 03d4h, 03b4h usage: Line compare register Description: Split screen, 8 bit value out of a ten-bit value ------------------------------------------------------------ Port-Index: 00h Port: 03c4h usage: Reset register d7-d2 Reserved d1 Synchronous reset d0 Asynchronous reset Description: Synchr. when set to zero, will halt and reset the sequencer at the end of its current cycle Asyncht. when set to zero, will immediatly halt and reset the sequencer. Data can be loss. ------------------------------------------------------------ Port-Index: 01h Port: 03c4h usage: Clock mode register d7,d6 Reserved d5 display off d4 Allow 32-bit Fetch (not used in standard modes) d3 Divide dot clock by 2 (used in some 320*200 modes) d2 Allow 16-bit fetch (used in mon graphics modes) d1 Reserved d0 Enable (0) 9 dot characters (mono text and 400-line) Description: Display off: Will blank screen and give the cpu uninterrupted access the display memory. ------------------------------------------------------------ Port-Index: 02h Port: 03c4h usage: Color plane write enable register d7,d6 Reserved d3 Plane 3 Write enable d2 Plane 2 Write enable d1 Plane 1 Write enable d0 Plane 0 Write enable Description: ------------------------------------------------------------ Port-Index: 03h Port: 03c4h usage: Character generator select register d7,d6 Reserved d5 Character generator table select A (MSB) d4 Character generator table select B (MSB) d3,d2 Character generator table select A d1,d0 Character generator table select B Description: This register is only of interest if your software will be using multiple character sets. Either one or two character sets can be active. Table A selects the charcater with attribute d3 set to zero and Table B is the one with d3 set to one. ------------------------------------------------------------ Port-Index: 04h Port: 03c4h usage: Memory mode register d4-d7 Reserved d3 Chain 4 (address bits 0&1 to select plan, mode 13h) d2 Odd/even (address bit 0 to select plane 0&2 or 1&3 text modes) d1 Extended memory (disable 64k modes) d0 Reserved Description: ------------------------------------------------------------ Port-Index: 00h Port: 03ceh usage: Set / Reset register d7-d4 Reserved (0) d3 Fill data for plane 3 d2 Fill data for plane 2 d1 Fill data for plane 1 d0 Fill data for plane 0 ------------------------------------------------------------ Port-Index: 01h Port: 03ceh usage: Set / Reset enable register d7-d4 Reserved (0) d3 enable set/reset for plane 3 (1 = enable) d2 enable set/reset for plane 2 (1 = enable) d1 enable set/reset for plane 1 (1 = enable) d0 enable set/reset for plane 0 (1 = enable) Description: Set/Reset enable defines which memory planes will receive fill data from set/reset register. Any plane that is disable for set/reset will be written with normal processor output data ------------------------------------------------------------ Port-Index: 02h Port: 03ceh usage: Color compare register d7-d4 Reserved d3 Color compare value for plane 3 d2 Color compare value for plane 2 d1 Color compare value for plane 1 d0 Color compare value for plane 0 Description: one indicate that color is the same ------------------------------------------------------------ Port-Index: 03h Port: 03ceh usage: Data rotate / Function select register d7-d5 Resrved (0) d4,d3 Function select d2-d0 Rotate count d4 d3 Function 0 0 Write data unmodified 0 1 Write data ANDed with processor latches 1 0 Write data ORed with processor latches 1 1 Write data XORed with processor latches Description: Rotation is made before writing data ------------------------------------------------------------ Port-Index: 04h Port: 03ceh usage: Read plane select register d7-d2 Reserved (0) d1,d0 Defines color plane for reading (0-3) Description: Doesnt matter in color compare mode ------------------------------------------------------------ Port-Index: 05h Port: 03ceh usage: Mode register d7 Reserved (0) d6 256-colour mode d5 Shift register mode d4 Odd / Even mode d3 Color compare mode enable (1 = enable) d2 Reserved (0) d1,d0 Write mode d1 d0 Write mode 0 0 Direct write (data rotate, set/reset may apply) 0 1 Use processor latches as write data 1 0 Color plane n (0-3) is filled with the value of bit n in the write data 1 1 Use (rotated) write data ANDed with Bit mask as bit mask. Use set/reset as if set/reset was enable for all planes Description: ------------------------------------------------------------ Port-Index: 06h Port: 03ceh usage: Miscellaneous register d7-d4 Reserved d3-d2 Memory map 00 = A000h for 128k 01 = A000h for 64k 10 = B000h for 32k 11 = B800h for 32k d1 Odd/even enable (used in text modes) d0 Graphics mode enable Description: Memory map defines the location and size of the host window ------------------------------------------------------------ Port-Index: 07h Port: 03ceh usage: Color don't care register d7-d4 Reserved (0) d3 Plane 3 don't care d2 Plane 2 don't care d1 Plane 1 don't care d0 Plane 0 don't care Description: Color don't care is used in conjunction with color compare mode. This register masks particular planes from being tested during color compare cycles. ------------------------------------------------------------ Port-Index: 08h Port: 03ceh usage: Bitmask register Description: The bitmask register is used to mask certain bit positons from being modified. ------------------------------------------------------------ Port-Index: - Port: 03c0h both index and data usage: d7,d6 Reserved d5 Palette address source 0 = palette can be modified, screen is blanked 1 = screen is enable, palette cannot be modified d4-d0 Palette register address Description: Palette register address selects which register of the attributes controller will be addres,sed by the next I/O write cycle ------------------------------------------------------------ Port-Index: 00h-0fh Port: 03c0h usage: Color palette register d6,d7 Reserved d5-d0 Color value Description: not used in 256 color modes ------------------------------------------------------------ Port-Index: 10h Port: 03c0h usage: Mode control register d7 p4,p5 source select d6 pixel width d5 Horizontal panning compatibility d4 Reserved d3 Background intensify / enable blinking d2 Line graphics enable (text modes only) d1 display type d0 graphics / text mode Description: p4,p5 source select: selects the source for video outputs p4 and p5 to the DACs. If set to zero, p4 and p5 are driven from the palette registers (normal operation). If set to one, p4 and p5 video outputs come from bits 0 and 1 of the color select register. pixel width: is set to one in mode 13h (256-color mode) horizontal panning compatibility: enhances the operation of the line compare register of the CRT controller, which allows one section of the screen to be scrolled while another section remains stationary. When this bit is set to one, the stationary section of the screen will also be immune to horizontal panning. ------------------------------------------------------------ Port-Index: 11h Port: 03c0h usage: Screen border color Description: In text modes, the screen border color register selects the color of the border that sorrounds the text display area on the screen. This is also referred to by IBM as overscan. Unfortunately, this feature does not work properly on EGA displays in 350-line modes. ------------------------------------------------------------ Port-Index: 12h Port: 03c0h usage: Color plane enable register d7,d6 Reserved d5,d4 Video status mux d3 Enable color plane 3 d2 Enable color plane 2 d1 Enable color plane 1 d0 Enable color plane 0 Description: The video status mux bits can be used in conjunction with the diagnostic bits of input status register 1 to read palette registers. For the EGA, this is the only means available for reading the palette registers. Enable color planes can be used to enable or disable color planes at the input to the color lockup table. A zero in any of these bit positions will mask the data from that color plane. The effect on the display will be the same as if that color plane were cleared to all zeros. ------------------------------------------------------------ Port-Index: 13h Port: 03c0h usage: Horizontal panning register d7-d4 reserved d3-d0 Horizontal pan Description: Horizontal pan allows the display to be shifted horizontally one pixel at a time. d3-d0 Number of pixels shifted to the left 0+,1+,2+ 13h Other modes 3+,7,7+ 0 1 0 0 1 2 1 - 2 3 2 1 3 4 3 - 4 5 4 2 5 6 5 - 6 7 6 3 7 8 7 - 8 9 - - ------------------------------------------------------------ Port-Index: 14h Port: 03c0h usage: Color select register d7-d4 Reserved d3 color 7 d2 color 6 d1 color 5 d0 color 4 Description: Color 7 and color 6: are normally used as the high order bits of the eight-bit video color data from the attribute controller to the DACs. The only exceptions are 256-color modes Color 5 and color 4: can be used in place of the p5 and p6 outputs from the palette registers (see mode control register - index 10h). In 16-color modes, the color select register can be used to rapidly cycle between sets of colors in the video DAC. ------------------------------------------------------------ Port-Index: - Port: 03c6h usage: Pixel mask register Description: ??? ------------------------------------------------------------ Port-Index: - Port: 03c7h usage: DAC state register (read-only) Description: if d0 and d1 is set to zero it indicates that the lookup table is in a write mode ------------------------------------------------------------ Port-Index: - Port: 03c7h usage: Lookup table read index register (Write only) Description: Used when you want to read the palette (set color number) ------------------------------------------------------------ Port-Index: - Port: 03c8h usage: Lookup table write index register Description: Used when you want to change palette (set color number) ------------------------------------------------------------ Port-Index: - Port: 03c9h usage: Lookup table data register Description: Read color value (Red-Green-Blue) or write same data. ========================================================================= = Shaggy member of The Yellow Ones = = = = E-Mail: D91-SJD@TEKN.HJ.SE ------------------- = = - Beaty is in the - = = Snail-Mail: Daniel Sjoberg - beholders eyes - = = Mogatan 11 - - = = S-56634 HABO - Charta 77 - = = SWEDEN ------------------- = =========================================================================