Display Interfacing with 8255

The most popular display is the Light emitting diode (LED) which is available in a variety of forms: single LED, bi-Colour LED, and Seven Segment LEDs.
Another popular display device is the Liquid Crystal Display (LCD), which is also gaining popularity because of its low power consumption.
There are many applications where you have to display numbers.
The most popular display device used for displaying numbers is seven- segment LED displays.
Seven Segment displays are used in number of systems to display the numeric information.
The seven segments can display one digit at a time.
Thus the number of segments used depends on the number of digits in the number to be displayed.
In each module, seven (eight including the display point.
LED segments are fabricated in a pattern as
The seven segments are numbered as a,b,c,d,e,f,g and the decimal point dp.
To reduce the number of pin counts, either all the cathodes are connected together inside the module providing
common cathode type display or
all the anodes are connected together providing
common cathode display.
Both the types are commercially available..
Depending on the type used, interface circuitry has to be made accordingly.
All hex characters from 0 to F can be conveniently displayed using seven segment LED displays as shown in figure.
One disadvantage of LED is that the readability of display becomes poor in bright light.
To improve readability, the display is covered with an amber colour plastic sheet.