1. Flowchart of basic interrupt mechanism
Fetch
Instruction
Increment PC
Decode and
Execute instr.
Int request line
active
Restore PC No
Yes
Interrupt
service
Routine
Store PC

2. Steps in handling interrupts
Disable further interrupts.
Store current state of program.
Execute appropriate interrupt handling routine.
Restore state of program.
Enable interrupts.
Resume program execution.

3. KEYBOARD INTERFACE BLOCK DIAGRAM
KB Data
Serial to Parallel Converter
PPI-Port A
PA0 - 7
Data Bus
KB Clock
Scan code
IRQ 1 ( Keyboard Interrupt)

4. Keyboard Connector 1- Keyboard Clock 2 – Keyboard Data 3 - Reset
4 – Ground
5 – Vcc (+5V) 1 2 4 5 3

5. RAM LOGIC
Contains the memory chips arranged as four banks of 9 chips each
Provided by using two banks of chips and two banks of 4164 chips
41256 & 4164 are both 16 pins Ics
41256 uses 18 bits address due to 256K locations
4164 uses 16 bits address due to 64K locations
The memory IC is organized internally as rows & columns.
The 4164 has memory cells in a 128 by 256 matrix.
There are two such matrix sections in a single 4164 i.e. 256 rows by 256 columns
The has same organisation but is repeated four times. i.e. 512 rows by 512 columns

6. IBM product introductions
MDA: introduced with IBM-PC in 1981
CGA: introduced as an option in 1982
EGA: introduced in 1984 (to replace CGA)
VGA: introduced in 1987 (as PS/2 option)

7. SHIFT REGISTER
Modulo 9
DISPLAY REFRESH
RAM
CHARACTER GENERATOR
ROM
Modulo 80+HR
MODULO 14
Modulo 25+VR

8. LCD Liquid Crystal Displays Advantages – Commonly used in laptops
Light weight
Thin profile
Low power dissipation
Commonly used in laptops
Two types of LCDs
Reflexive Type
Transmission Type

9. Reflexive Type LCDs Low power But Disadvantages-
Low contrast
Relatively narrow viewing angle
Only monochrome displays
Method to improve these displays is to use different shades of grey color
82C455 graphics controller from Chips and Technologies contains all the circuitry needed to interface with CGA, VGA and EGA LCD displays with grey scaling

10. How The Video Card Works
The Video Card is a circuit. It is responsible for processing video data from the CPU so that the monitor can understand it and create a picture on the screen. The Video Chipset, the Video Ram and the Digital Analog Converter are all things that are used to do this.

11. How The Video Card Makes A Picture
First, the Video data is transferred from the CPU to the Video cards chipset it then processes the data. The data is then transferred from the Video chipset to the Video Memory. The video memory stores the image. The data is then transferred from the video memory to the digital analog converter. The digital analog converter converts the image from digital data to analog data. The analog data is then transferred to the monitor through whatever cable it is using. For example, VGA, DVI, S-Video, or HDMI cables.

12. Transmission Type LCDs
Used in portable computers
A strong fluorescent backlight is passed through LCD elements & some filters to produce desired displays.
Color of pixel is determined by a triad consisting of red, green and blue elements.
Disadvantages-
High cost
Large amount of power used by backlight
Hence limits their use in battery powered laptops.

14. CGA - OPERATING MODES MODES RESOLUTION COLORS/PALETTE ALPHA
25 X 80 (8 X 8)
4 /16
2. LOW RESOLUTION
160 X 100
3. MEDIUM RESOLUTION
320 X 200
4. HIGH RESOLUTION
640 X 400

15. Character Generator ROM Alpha Serializer Pallete/ Overscan I
Processor address
Display Buffer
Address Latch
Input Buffer
Processor data
Address Latch
Data Latch
Data Latch
6845 CRTC
Output Latch
Processor data
Color Encoder R
Graphics Serializer G B
Character Generator ROM
Alpha Serializer
Pallete/
Overscan I
HSYNC/VSYNC
Mode Control
Timing generator & Control
Composite Color Generator
Comp. Video

16. CGA screen resolutions
color: 320x200 (4 packed pixels-per-byte)
memory: 320x200/4 = bytes
mono: 640x200 (8 packed pixels-per-byte)
memory: 640x200/8 = bytes

17. EGA - OPERATING MODES MODES RESOLUTION COLORS/PALETTE ALPHA
25 X 80 ( 8 X 14)
4 /16
2. LOW RESOLUTION
160 X 100
3. MEDIUM RESOLUTION
320 X 200
4. HIGH RESOLUTION
640 X 400
5. HIGH RESOLUTION
640 X 350
16 / 64

18. EGA display modes New display modes 13, 14, 15, 16
13: 320x200 with 16-colors
14: 640x200 with 16-colors
15: 640x350 2-colors (monochrome)
16: 640x350 4-colors w/64K vram or 16-colors w/128K vram
But uses “planar” memory organization, so relies on “Graphics Controller” hardware

19. The EGA’s 16-color palette
4-bits
A 4-bit pixel-value from planar vram
selects a color from the palette to
draw onto the display screen
“planar” vram
Color palette (16 colors)
Display screen

20. EGA 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 D3 D2 D1 D0
FRAME BUFFER

21. VGA - OPERATING MODES MODES RESOLUTION COLORS/PALETTE ALPHA
25 X 80 ( 8 X 16)
4 /16
2. LOW RESOLUTION
160 X 100
3. MEDIUM RESOLUTION
320 X 200
4. HIGH RESOLUTION
640 X 400
5. HIGH RESOLUTION
640 X 350
16 / 64
6. HIGH RESOLUTION
640 x 480
16/256k
7. HIGH RESOLUTION
320X 200
256 / 256k

22. Video Graphics Array (VGA)
Offers both CGA and EGA emulation
And supports three new display modes:
mode 17: improved monochrome graphics
mode 18: 16-colors using “square” pixels
mode 19: supports 256 colors (8 bits/pixel)
Provides faster display-refresh rates
Supports analog multisync monitors

23. VGA 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 D8 D2 D1 D0
Display Memory

24. VGA 18-bit color registers Palette Register 0 - 3 255 0 - 363 64
127
255
0 - 3
0 - 3
Display Memory
4 - 7
Part ( A)

25. VGA 18-bit color registers Palette Register 255 Bank0 Bank1 0 - 363 64
127
255
Bank0
Bank1
0 - 3
Bank2
Display Memory
0 - 5 C7 C6
Bank3
6 -7
Color Select Register
Bank Select

26. VGA 18-bit color registers Palette Register 255 Bank0 Bank1 0 - 315 16 31
255
Bank0
Bank1
0 - 3
Bank2
Display Memory
0 - 3 C7 C6 C5 C4
Bank15
4 -7
Color Select Register
Bank Select

28. SVGA
SVGA is an acronym for Super Video Graphics Array and covers a wide range of computer display standards used in the manufacture of computer monitors and screens.
The SVGA standard was designed by VESA, the Video Electronics Standards Association.
When using SVGA as a direct comparison to other display standards such as XGA (Extended Graphics Array) or VGA (Video Graphics Array) the standard resolution referred to as SVGA is 800*600 pixels.
When the SVGA standard was first defined it referred to a resolution of 800*600 4-bit pixels (total number of pixels would be 480,000) which means that each pixel could be one of 16 different colors. This definition was quickly extended to 1024*768 8-bit pixel resolution, meaning that there is a choice of 256 colors.
As technology has advanced, the number of colors has become irrelevant as it is now set by a varying analog voltage that indicates the shade of the color, meaning that a SVGA monitor is theoretically capable of displaying an unlimited number of colors. However as the internal workings of the video card are digital, this places a finite limit on the number of colors that can be displayed. For example a monitor may be capable of displaying any color from a palette of 16 million, but the video card could limit this to displaying only 256 colors simultaneously due to memory restrictions. Almost all monitors produced between the late 1990s to the early 2000s are SVGA monitors, making SVGA more of an umbrella term than a fixed standard.
When VGA was introduced the video interface between the adaptor and the monitor changed from digital to analog, giving the effectively infinite color range. Therefore color depth became largely a function of how the video adapter was constructed and not the monitor, so the same monitor connected to different video adaptors would give different performance.
So although SVGA is a widely used term, it has no specific definition in terms of resolution or bit depth. In general use, SVGA is used to describe a display capability generally somewhere between 800×600 pixels and 1024×768 pixels at color depths ranging from 8 bits (256 colors) to 16 bits (65,536 colors).