COE205

1

• COE-205
• Computer Organization Assembly Language
• Section 56
• Experiment11

2
Outline

• Review
• Accessing Video Memory

3
How Monitor Works

• How do you think the monitor works?

4
How Monitor Works

• How do you think the monitor works?

Pixel
Video Memory
Refresh Rate
5
More Details

• Size of the Pixel determines_________?
• Screen Resolution determines _________?

6
More Details

• Size of the Pixel determines the number of colors
  to represent
• Screen Resolution determines _________?

7
More Details

• Size of the Pixel determines the number of colors
  to represent
• 2 colors (1white 0black)
• 256 colors
• Screen Resolution determines _________?

1-bit
8-bit
8
More Details

• Size of the Pixel determines the number of colors
  to represent
• 2 colors (1white 0black)
• 256 colors
• Screen Resolution determines the size

1-bit
8-bit
9
Screen Resolution

• 32-bit
• Example
• Memory Needed ?

10
Screen Resolution

• 32-bit
• Example
• Memory Needed 800 X 600 X 32 1.83 MB

11
Video Modes

• Text Mode
• Example 0000 1111 1000 0001
  0741H
• Graphics Mode
• 
  1110

Background
Foreground
ASCII Code
Color Code
A
Color Code
Example
12
Color Codes
13
MS-DOS Video Modes

• Text Mode
• 80 X 25 screen
• Pixel 16-bit (textcolor)
• Located at B8000000
• Graphics Mode
• 640 X 480 screen
• Pixel 16-bit
• Located at A0000000
• 
  

14
Types of Access

• Direct Access
• Reading/writing bytes to B800 or A000
• Through Interrupts
• INT 21H, 12H, 10H

15
10H Family