Wednesday 28 September 2011

KEYBOARD AND DISPLAY INTERFACE - 8279


KEYBOARD AND DISPLAY INTERFACE - 8279

AIM:
            To write a program to study 8279 Keyboard and display controller and also initialize 8279 for rolling message in the display.
 APPARATUS REQUIRED:
            1. 8085 – Microprocessor kit        
            2. 8279 – Keyboard and display controller board
            3. Flat ribbon cable
ALGORITHM:
DISPLAY THE ROLLING MESSAGE:
1. Start the program
            2. Set mode and clear display is given to initialize the 8279
            3. The data to be displayed is moved to a register
            4. Initialize the counter value
            5. Increment the address, which is to be displayed and display the next value
            6. Decrement the counter value
            7. Delay the sequence of data that are displayed for a lively display
1.      End of the program

DESCRIPTION:    
            In the 8279 Keyboard and display interfacing we have to initialize it through the keyboard / display mode set by which we adopt the mode by which we are going to operate the clear display is executed to clear all the rows of the display RAM the data which is to be displayed is fetched and then thus are displayed is fetched and then thus are displayed at first digit of display a counter is initialized and its value is decremented until all the values are displayed A delay which is set such that the display it is delayed for a period such that to get a lively display the write display RAM Command word is used it set the auto increment flag.
 PROGRAM
            ROLLING DISPLAY:
                                    ORG 4100 H             CNT EQU OCZH
                                    DAT EQU OCOH     POINTER EQU 412CH
ADDRESS
OPCODES
LABELS
MNEMONICS
COMMENTS
4100
21,2C, 41
START
LXI H, POINTER
Set the point for data in array
4103
16,OF

MVI D, 0F H
Move immediate D register
4105
3E, 10

MVI A, 10H
Move 10 to A register
4107
D3, C2

OUT CNT
Set mode of display
4109
3E,CC

MVI A, OCCH
Clear display
410B
D3, C2

OUT CNT
Out the control word
410D
3E, 90

MVI A, 90H
Write display
410F
D3, C2

OUT CNT

4111
7E
LOOP
MOV A, M
Move the HL pair to accumulator
4112
D3, C0

OUT DAT
Clear loop RAM
4114
CD, 1F, 41

CALL DELAY
Call display 411f
4117
23

INX H
Increment HL pair
4118
15

DCR D
Decrement D register
4119
C2, 11,41

JNZ LOOP
Jump on zero
411C
C3, 00,41

JMP START

411F
06,A0
DELAY
MVI B, OFFH

4121
0E,FF
LOOP1
MVI C, FFH


4123
0D
LOOP2
DCR C
Decrement C register
4124
C2, 23,41

JNZ LOOP2
Jump on zero
4127
05

DCR B
Decrement B register
4128
C2, 21,41

JNZ LOOP1
Jump on zero
412B
C9

RET
Return
412C
FFFFFFFF



4130
FFFFFFFF



4134
98687CC8



4138
1C29FFFF




ROLLING DISPLAY:
                        HELP US
H – a=0, b=1, c=1, D=0, e=1,f=1, g=1      E – a=1, b=0, c=0, D=1, e=1, f=1, g=1
L – a=0, b=0, c=0, D=1, e=1, f=1, g=0     P – a=1, b=1, c=0, D=0, e=1, f=1, g=1
U – a=0, b=1, c=1, D=1, e=1, f=1, g=0     S – a =1, b=0, c=1, D=1, e=0, f=1, g=1

RESULT:
Thus the Program of Interfacing 8279 Keyboard and display is executed and verified.

1 comments:

Unknown said...

We want 8086 interfacing with 8279

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