Statement: Interface a 64-key matrix keyboard to the 8085 microprocessor using 8255. Write an 8085 assembly language program to initialize 8255 and to read the key code.
HARDWARE FOR MATRIX KEYBOARD INTERFACE
Fig. shows a matrix keyboard with 64 keys connected to the 8085 microprocessor using 8255. A matrix keyboard reduces the number of connections, thus the number of interfacing lines. In this example, the keyboard with 64 keys, is arranged in 8 x 8 (8 rows and 8 columns) matrix. This requires sixteen lines from the microprocessor to make all the connections instead of 64 lines if the keys are connected individually. The interfacing of matrix keyboard requires two ports: one input port and other output port. Rows are connected to the input port, port A and columns are connected to the output port, port B.
SOFTWARE FOR MATRIX KEYBOARD INTERFACE
As port A is used as an output port, control word for 8255 is 80H.
Flowchart for Source Program
Related Programs (Click down)