Deluxe Text Display Adapter  (250-3046)   Programming   Faxback Doc. # 2143

The following information is used to set the MODE Registers:

DTDA REGISTER VALUES
   ┌───────────────────┬─────────────────┬─────────────┐
   │ Resolution:       │     80 x 25     │     80 x 25 │
   │ Adapter Mode:     │ Monochrome Text │ Color Text  │
   ├───────────────────┼─────────────────┼─────────────┤
   │ R0--HOR TOTAL     │     61          │     61      │
   │ R1--HOR DISP      │     50          │     50      │
   │ R2--HYSNC POSN    │     52          │     52      │
   │ R3--HS WIDTH      │     0F          │     0F      │
   │ R4--VERT TOTAL    │     19          │     19      │
   │ R5--VERT ADJ      │     06          │     06      │
   │ R6--VERT DISP     │     19          │     19      │
   │ R7--VSYNC POSN    │     19          │     19      │
   │ R8--INTERLACE     │     02          │     02      │
   │ R9--MAX SCAN      │     0D          │     0D      │
   │ R10--CUR START    │     0B          │     0B      │
   │ R11--CURSOR END   │     0C          │     0C      │
   │ R12--START (H)    │     00          │     00      │
   │ R13--START (L)    │     00          │     00      │
   │ R14--CURSOR (H)   │     00          │     00      │
   │ R15--CURSOR (L)   │     00          │     00      │
   │ MODE REG          │     29          │     2D      │
   └───────────────────┴─────────────────┴─────────────┘

Notes: 

* All values given are in HEX.
* Use CRTC I/O addresses 3B4 (register number) and 3B5 (register value)

MODE register I/O address of 3B8

Available Colors

Color Code   Screen Color      Color Code   Screen Color

    0        Black                 8        Dark Gray
    1        Blue                  9        Bright Blue
    2        Green                10        Bright Green
    3        Cyan (pale blue      11        Bright Cyan
    4        Red                  12        Bright Red
    5        Magenta (purple      13        Bright Magenta
    6        Yellow               14        Bright Yellow
    7        White                15        Bright White

Blinking Text:

The background intensity bit (80 of ODD bytes) in the video display word is 
shared with the character BLINK logic. If bit 20 of the MODE register is a 0, 
then all 16 colors are available for character backgrounds. If the bit is set 
to a 1, the background intensity bit (80) is changed to be a BLINK CHARACTER 
bit.

Mode Control Register:

Bit  Function

08   VIDEO ENABLE--When set to a "0" the video displays are turned off. The 
     monochrome display SYNC signals are set to the OFF state and all video 
     outputs are turned off.

20   BLINK ENABLE--When set to "0" text characters can not blink. When set to 
     a "1" the BACKGROUND INTENSITY bit (80) of the display RAM character 
     attribute byte will control the blinking of the character (if set, the 
     character will blink).

Text Mode:

The even byte of each word contains the number of the character to display. 
The IBM standard character set contains 256 unique characters numbered from 
0-255.

The odd byte (attribute byte) determines the shade of the character dots and 
their surrounding background. The lower four bits contain the color code of 
the character's dots. If bit 0 (B) is set to a 1, then underline is enabled. 
The upper four bits determine the color of the dots in the character matrix 
that determine the color of the dots in the character matrix that surround 
the character outline.

Even Byte Character Code:

Bits:  7   6   5   4   3   2   1   0
       character code 00-FF

Bits:  7   6   5   4   3   2   1   0
       I   R   G   B   I   R   G   B

       BACKGROUND        FOREGROUND

Sixteen unique colors are available for the foreground or background. These 
colors are formed by combining the basic colors Red, Green, and Blue with an 
optional intensity bit.