LED INTERFACE.ppt

LED INTERFACE

1. LED INTERFACE

2. INTRODUCTION
•LightEmittingDiodes(LEDs)areusedtodisplaylimited
data,results,etc.,
•Thelightemittingdiodeisadiodewhenconducts,emitslight
energy.Theconductionstartswhentheanodeisheldathigher
voltagethanthecathode.

3. CONTD..
•Incommoncathodeconfigurationwheneverabitis1,the
correspondingLEDwillglow.
•Incommonanodeconfiguration,a0inanybitpositionwill
makethecorrespondingLEDglow.
•Sobyloadingaparticularbitpatternintheport,thedesired
LEDmaybelighter.
•Thestructuredhaseightsegmentsmarkeda,b,c,d,e,fandhand
itisveryusefulinthedisplayofthenumericandalpha
numericdata.

4. FIG : SEVEN SEGMENT LED AND ITS
CONTROL BYTE FORMAT

5. PARALLEL INTERFACE

6. CONTD..
•TheparallelinterfacebetweenthesevensegmentsLED
displayisshowninthepreviousfigure.
•TheanodeofallLEDsareheldpermanentlyat+5v,whereas
thecathodesareconnectedtotheportbits.The
Microprocessorwillloadanybitpatternintheoutport.
•Theserialinterfaceovercomesthebelowdisadvantages.
DISADVANTAGES :
1.)Itrequiresextrahardwareforinterfacing.
2.)Softwareisverysimple.
3.)Itrequiresextraports.

7. SERIAL INTERFACE

8. SEVEN SEGMENT LED DISPLAY
INTERFACE TO THE 8085 USING THE 8255