AH = 62h: Set/Read Display Contrast

This function sets or reads the contrast register. The range of permissible values is 0 - 1Fh. The highest display contrast corresponds to a value of 1Fh.

• Input: AH = 62h
  AL = Subfunction
  = 0 - Set Contrast value in BL
  =1 - Read Contrast value and return it in AL
  BL = 0-1Fh Contrast value (If AL=0)
  > 1Fh Contrast value set to 1Fh

• Output: AL = contrast value if AL was 1 at entry
• Registers modified: AX