Problem – Interface 8255 with 8085 microprocessor and write an assembly program which determine the addition of contents of port A and port B and store the result in port C.
- Construct the control word register
- Input the data from port A and port B
- Add the contents of port A and port B
- Display the result in port C
|MVI A, 90||A ← 92|
|OUT 83||Control Register ← A|
|IN 80||A ← Port A;|
|MOV B, A||B ← A;|
|IN 81||A ← Port B;|
|ADD B||A ← A+B;|
|OUT 82||Port C ← A|
- MVI A, 92 means that the value of control regidter is 92.
D7=1 as it is in I/O mode. D6=0 & D5=0 as Poet A is in m0 mode. D4=1 as Port A is taking input. D3=0 & D0=0 as Port C is not taking part. D2=0 as mode of Port B is m0. D1=1as Port B is taking the input.
- OUT 83 putting the vaue of A in 83H which is the port number of port control register.
- IN 80 taking input from 80H which is the port number of port A.
- MOV B, A copies the content of A register to B register.
- IN 81 take input feom 81H which is the port number of port B.
- ADD B add the contents of A register and B register.
- OUT 82 displaying the result in 81H which is the port number of port C.
- RET return