Interfacing Display with MPU without Peripheral Controller

Dr A SahuDept of Computer Science & Engineering

IIT Guwahati

Outline• Peripheral communications • Display• LED Display– Decoder – Generic model– Interfacing

• Character Display Monitor– Decoder– Generic Model

• Graphics monitor – Why graphics? Vector Vs Raster

• Keyboard type and Interfaces

Introduction

• Peripherals : HD monitor, 5.1 speaker • Interfaces : Intermediate Hardware – Nvidia GPU card, Creative Sound Blaster card

• Interfaces : Intermediate Software/Program– Nvidia GPU driver , Sound Blaster Driver software

Processor RAM

Transmission controller• Transmission Controller:– MPU control, Device Control (DMA)

• Type of IO mapping– Peripheral (IN/Out), Memory mapped IO (LD/ST,MV)

• Format of communication– Synchronous (T & R sync with clock), Asynchronous

• Mode of Data Transfer – Parallel, Serial (UART)

• Condition for data transfer – Uncond., Polling, Interrupt, Ready signal, Handshake

Display

7 Seg 9 Seg 16 Seg 3x5 DotMatix 5x7 9x11

Dot Matrix Display Panel 25x80 character monitor

Generic Model (Data) of Display

DataASCII/BCD

DecoderOr

Memory

Display

Monitor/LEDs

Time to Decode Time to Display

7 Segment LED Interfaces

• Data to 7 Segment Decoder

a

b

c

d

e

f

g

Common Cathode

a

b

c

f

g

e

d

D

C

B

A

LT

RBI

BI

Decoder

5V

1

0

0

0

1

01

1

10

1

5

5v

5V

1

11

1

11

1

5

5v

RBO

Multiple 7 Segment LED Interfaces

• Data to 7 Segment Decoder

a b c d e f g

D C B A

RBI RBO

a b c d e f g

D C B A

RBI RBO

a b c d e f g

D C B A

RBI RBO

a b c d e f g

D C B A

RBI RBO

a b c d e f g

D C B A

RBI RBO

5V

0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 1 1 1

10

Blank

0

Blank

1 1

Multiplexed line and Memory use

40 Bit data line

8 Bit data line

0 1 2 3 4

Data 1 Data 2Data 3Data 4

Data 0

Mod 5 Counter

Multiplexed line/Memory used 7 Segment Decoder

1:N Decoder

Counter

RAM

590

Interface LED Display Using Delay

• Write a program to display contents of B,C,D and E register to LED display

• Write to buffer memory to display to 7 Seg. LEDs

• Use address FC H,FD H,FE H and FF H to display

Interface Diagram

LEDsBuffer

Memory

Address line

CS WR RD

Datalines

Ctr

7 Seg.Decoder

MPU

A7

A6

A5

A4

A3

A2

74LS373Latches

LED7

D6

D5

D4

D3

D2

D1

D0

A1

A0

IO/MRD

WR

Monitor program

• Interface program to Display content of B,C,D and E after 1 Sec Delay

DIS: MVI A,BOUT FCHMVI A,COUT FDHMVI A,DOUT FEHMVI A,EOUT FFHCALL DELAY ;1sec delay JMP DIS;

Multiplexed 25x80 Char Display

25x80 character monitor

C A T

F I R E

0 1 2 3 4 ….. 78 79012

2324

A

DecoderOr

ROMMemory

Decoded Bits

Row Ctr

ColCtr CLK > 50Hzx25x80

Generic Model of Char Monitor

• Delay of Monitor is 1/50 Sec, After Every 50 Second it makes ready

• From stream buffer it writes to Frame buffer after getting command. (Flush stream command)

Char FrameBuffer

Memory

Address line

CS WR

Datalines

Counter

Stream Buffer

When C=0Ready

Address (r,c)

Speed of Display• LED is very high speed – You can write to LEDs at very high speed– Display meant for to see some thing (Is it good?)

• 30 Frames/Sec is more then enough for human eye (>30 blink make human eye Fixed)

• No of blink > 30Hz – Human can not differentiate ON/OFF state, it will

be seen AS ON state• Video display make default 30-60 Frame/Sec• Monitor run at speed 30-60 Frame/Sec

Speed of Monitor and Disk

• Speed is fixed (60Frame/Sec)

• $ a.out• $ a.out > outputfile• $ a.out > /dev/null

for(i=0;i<10000;i++){printf(“HelloWorld”);

}

Migration from Char to Graphics/Video

• Char display (80x25 char, 5x7pixel=400x175)• CRT Monitor (400x600, 640x480,600x800)• LCD Monitor (1024x768,1280x1024,…)• Graphics visually more appealing • Display Line, Circle, Rectangle, Curve, Polygon– Character using this primitives– True type font

RED ARROWCircle

Multiplexed 1024x768 pixel display

1024x768 Pixel LCD

0 1 2 3 4 ….. …1023012

767

R

Row Ctr

ColCtr CLK > 1024x768x50Hz

B G8x3=24 Bits

Frame Buffer

Refresh screen 50 time a Sec

Frame Buffer (1 Bit Pixel): Grey

Pixels in Frame Buffer

1 Bit Per Pixels Pixels on the Screen

Graphical representation of 1 bit color

Frame Buffer (15 Bit Pixel)

Pixels in Frame Buffer

Pixels on the Screen

15 Bit Per Pixels

Graphical representation of 15 bit color

Frame Buffer (24 Bit Pixel)

Pixels in Frame Buffer

Pixels on the Screen

24 Bit Per Pixels

Graphical representation of 24 bit color

1bit, 8 bit & 16 bit color

1- bit color 8-bit color 16-bit color

Graphics

• Vector graphics: – Use geometrical primitives based

on mathematical equations, to represent images in computer graphics

– Points, Lines, Curve, shapes or Polygons

• Raster Graphics: Complementary to Vector Graphics– Representation of images as an

array of pixels – photographic images

Vector graphics• Store the primitives in the FILE– Word, Photoshop, Xfig, GNUPlot, PS, HTML Tag

• Raster: Store the Pixel values in the FILE– BMP, PNG, JPG

• At runtime, process the primitive and generate Pixel to raster the screen (Display)

• Who do this?– Software – GPU (hardware accelerated routine)

Character Vs Font • Computer font formats: TrueType Font – Where each letter is created from Bézier curves

• Many varieties of font for a characterUnits

Points with unit and curve

properties are stored

Graphics Cards• GPU : specialized processor that accelerates

3D or 2D graphics primitives operations• Lots of Floating point operations• Accelerates Primitives – Line, circle, polygon, mesh, projection, sphere,

Graphics System 3D application

3D API: OpenGL

DirectX/3D

3D API Commands

CPU-GPU Boundary

GPU Command& Data Stream

GPU Command

PrimitiveAssembly

Rastereisation Interpolation

RasterOperation

Frame Buffer

Programmable Fragment Processors

ProgrammableVertex

Processor

Vertex Index Stream

Assembled polygon, line & points

Pixel Location Stream

Pixel Updates

Transformed Fragments

Rastorized PretransformedFragments

transformedVerticesPretransformed

Vertices

Graphics System

Memory System

Texture Memory

Frame Buffer

Vertex Processing

Pixel Processing

Vertices(x,y,z)

PixelR, G,B

Vertex Shadder

Pixel Shadder

Keyboard

Reference • R S Gaonkar, “Microprocessor Architecture”, Unit II preface,

Chapter 14 and 17

Thanks