Video systems

Lesson plan

Review the code for the previous exercise

Video systems

Review for midterm exam

Midterm exam

Thursday,March 16, 2004.

Include:Multiple choice

Fill-in the blank

Problem solving

Last practice exercise

MOV AX,DATASEG ;Set address of data MOV DS, AX

MOV AH, 0AH ;Get inputsLEA DX, Para_listINT 21H

MOV BH, 00 ;Add ‘$’ to the endMOV BL, act_len ;of the input stringMOV input[BX+1],'$'

Last practice exercise

MOV AH, 02H ; set cursorMOV BH, 0 ; page# to BHMOV DH, 12 ; row# to DHMOV DL, 40 ; column# to DLINT 10H MOV AH,09H ; display the stringlea dx, inputint 21h

Video systems

Components of a video system

Monitor

Monitor SignalGenerator

CharacterGenerator

Mode Control

Video controller

Attribute Decoder

Video displayArea

Video systems

MonitorConsists of a group of closely-spaced horizontal lines (raster)Each line consists of pointsEach points consists of three luminescent phosphor dots

Video Display AreaIs the area in memory to contain data for text and graphic mode (buffer)Address depends on the type of video adapter and chosen mode

Video systems

Video display area:A0000H: font descriptors

B0000H: monochrome text for mode 07H

B8000H:Text and graphic modes

Allows store data in pages

Video controllerGenerates horizontal and vertical timing signals

Video systems

Video BIOS:Acts as an interface to the video adapter contains routines as setting the cursor and displaying characters

Video RAM bios supports two Video Data Areas:

40:[49H]: current mode, #columns, size

40:[84H]: #rows and height

Video systems

Video modes (text and graphic modes)

Mode Type Area Page

07 Monochrome B000 0

03 Color B800 0-3

Attributes

Attribute byte in text mode determines the characteristics of each displayed characters

Background Foreground

Black Blue 01HBlue Red 14HGreen Cyan 23HWhite Light magenta 7DHGreen Gray A8H

BIOS INT 10H

We have learned INT 10H to:

This week, we use this 10H

to manage screen, cursor, pages

Clear screenSet cursor

Set video mode

Step 1: Set AH=00HStep 2: Load video mode to AL (see video mode on page 156)Step 3: Call INT 10H

Example:MOV AH, 00HMOV AL, 00H ;Text mode 40x25INT 10H

Video mode supported by EMU8086

00h - text mode. 40x25. 16 colors. 8 pages.

03h - text mode. 80x25. 16 colors. 8 pages.

13h - graphical mode. 40x25. 256 colors. 320x200 pixels. 1 page

Set cursor size

Step 1: Set AH=01HStep 2: Set CH=start scanning lineStep 3: Set CL =end scanning lineStep 4: Call INT 10H

Start scanning line: [0,13]End scanning line:[0,14]when bit 5 of CH is set to 0, the cursor is

visible. when bit 5 is 1, the cursor is not visible.

Set cursor size

Example:MOV AH, 01H

MOV CH, 00H

MOV CL, 07H

INT 10H

Get cursor status

• Cursor status include: row, column and size of the cursor

Step 1: Set AH=03H

Step 2: Set BH= page number

Step 3: Call INT 10H

Step 4: Return values at DH=Row, DL=Column, CH= Starting scan line and CL= Ending scan line

Get cursor status

Example

MOV AH, 03h

MOV BH,0

INT 10H

Scroll up screen

• Step 1: Set AH=06H, Set AL= number of rows

• Step 2: Set BH= Attribute or pixel value

• Step 3: Set CX: starting row:column

• Step 4: Set DX: ending row:column

Scroll up screen

• Example:MOV AX, 602H ; AH=06H, AL=02H

MOV BH, 61H ; Brown background, ; Blue foreground

MOV CX, 0000H

MOV DX, 184FH ; Scroll full screen

INT 10H

Scroll down screen

Step 1: Set AH=07H, AL=00H

Step 2: Set BH=attribute or pixel value

Step 3: Set CX=Starting row:column

Step 4: Set DX=Ending row:column

Scroll down screen

Example:MOV AX, 702H ; AH=06H, AL=02H

MOV BH, 61H ; Brown background, ; Blue background

MOV CX, 0000H

MOV DX, 184FH ; Scroll full screen

INT 10H

Display character and attribute at cursor

Step1: Set AH=09H

Step 2: Set AL=character to display

Step 3: Set BL = attribute or pixel value

Step 4: Set BH= page number

Step 5: Call INT 10H

Display character and attribute at cursor

Example:

MOV AH, 09H

MOV AL, 41H

MOV BL, 16H

MOV BH, 0

MOV CX, 10

INT 10H

Read character and attribute at Cursor

INT 10H Function 08H

MOV AH, 08H

MOV BH, 00

INT 10H

The character will be stored at AL and its attribute is stored in AH

Review midterm exercise

Review chapter 8

Read Character Generator Data

INT 10H function 11H and subfunction 30H

Example

Step 1: Set AH=11H and AL=30H

Step 2: Set BH=0; code 0,1,2..7

Step 3: Call INT 10H

Display character string

INT 10H, function 13HStep 1: Set AH=13HStep 2: Set AL=subfunction(00,01,02,or 03)Step 3: Set BH=page numberStep 4:Set BL=attributeStep 5: Set BP=address of the string (ES:BP)Step 6: Set CX=lengthStep 7: Set DX=row:columnStep 8: Call INT 10H

Display character stringExample:

MOV AL, 1 MOV BH, 0 MOV BL, 00111011bMOV CX, 10;MOV DL, 10MOV DH, 7PUSH DSPOP ESLEA BP, offset messageMOV AH, 13h int 10h

Answers for review exercise

1. On the display screen, the row:column (a) for the upper left corner is numbered _00_H:__00__H; (b) for the upper right corner is _00__H:_4F_H; (c) for the lower left corner is _18__H:_00__H; (d) for the lower right corner is _18___H:_4F_H.

Answers for review exercise

2. INT 10H_ is the BIOS operation for screen handling, and function 02__ in AH tells the operation to set the cursor. Page number, normally 0_, is in the _BH__ register, and row and column are in the _DX__ register.

Answers for review exercise

3. For screen clearing or scrolling, use BIOS INT 10H__ and insert function _06H_ in AH, _00__ for full screen in AL, _attribute___ in BH, starting row:column______ in CX, and ending row:column_____ in DX.

Answers for review exercise

4. INT 21H function 09H for displaying requires defining a display string in the data area, immediately followed by the __$____ character.

Answers for review exercise

5. For INT 21H function 0AH, the area for keyboard input requires definition of a _parameter_ _list___. The first byte contains maximum number of character entered_. The second byte is for the operation to store the __actual number of character entered_. The third byte begins a field that is to contain _entered ______ _characters_________.

Answers for review exercise

6. INT 21H function _40H__ for file handles requests display. Load file handle 01 in the _BX__ register, the number of characters to display in the _CX__ register, and the address of the area to display in the _DX__ register.

Answers for review exercise

7. The hex character for Tab is _09H_, for Line Feed is _0AH_, and for Carriage Return is _0DH_.

Answers for review exercise

This code uses the instructions for INT 21H function 40H to display the message "Informatics Computers" followed by a Carriage Return and Line Feed, to begin displaying at row 02, column 18.

Week 5 review

A _short_____ address is limited to a distance of -128 to 127 bytes. A _near_____ address is limited to a distance of 32,768 to 32,767 bytes within the same segment. A _far___ address is one that is (usually) in another segment and is reached by a segment:offset value.

Week 5 review

The LOOP instruction requires an initial value in the _CX__ register. For each iteration, LOOP deducts 1 from this value; if it is __zero______, control drops through to the following instruction, and if it is _nonzero______, control jumps to the operand address.

Week 5 review

The _CALL___ instruction transfers control to a called procedure and the RET___ instruction returns from the called procedure to the original calling procedure.

Week 5 review

A CALL to a procedure within the same segment is _near___ (short/near/far) and decrements the _SP__ register by 2, pushes the _IP__ register (containing the offset of the instruction following the CALL) onto the stack, and inserts the offset address of the called procedure in the _IP_ register.

Week 5 review

A RET instruction that returns from a near procedure pops the original value from the stack into the _IP__ register and increments the _SP__ register by 2.

Week 5 review

AX= 0 CX=5AX=AX+BX = 0+25 CX=4AX=AX+BX =0+25+25 CX=3AX=AX+BX=0+25+25+25 CX=2AX=AX+BX=0+25+25+25+25CX=1AX=AX+BX= 0+25+25+25+25+25CX=0 (quit)AX= 25*5 = 125