🚀 go-pugleaf

Goal:
  The following code is supposed to switch a standard VGA
  display on my PC (running DOS, but that shouldn't matter)
  between blinking text and light background colors.

Problem:
  Reading the contents of attribute controller (ATC)
  register 10h doesn't seem to work. Line graphics mode
  always gets turned off.

Question:
  Can you tell me what changes I have to make to make the ATC read work?

C-Code:

  void blink (int on) {
  /* 0 -> allow light background attributes  */
  /* 1 -> make text blink instead            */

    unsigned char reg10;

    reg10 = inportb (0x3da);         /* set ATC to index mode */
    outportb (0x3c0, 0x10|32);       /* select mode control register */
    reg10 = inportb (0x3c1);         /* read current status (!) */
    if (on) reg10 = reg10 | 8;       /* set bit 3 (blink on) */
    else asm {and reg10, 11110111b}; /* clear bit 3 (blink off) */
    outportb (0x3c0, 0x10|32);       /* reg select */
    outportb (0x3c0, reg10|32);      /* write changes */
  }

When I set the register contents manually, it works fine, so
I believe that the write operation poses no problem.

Please reply by e-mail, too. Any help would be most appreciated!
Thanks!
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 Thomas Jensen <fi136@fim.uni-erlangen.de> 2B |! 2B  W.S.
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