Interface 8255 with 8085 microprocessor for addition
Problem – Interface 8255 with 8085 microprocessor and write an assembly program that determines the addition of contents of port A and port B and stores 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, 92H||A ← 92|
|OUT 83H||Control Register ← A|
|IN 80H||A ← Port A;|
|MOV B, A||B ← A;|
|IN 81H||A ← Port B;|
|ADD B||A ← A+B;|
|OUT 82H||Port C ← A|
- MVI A, 92H means that the value of the control register is 92.
D7=1 as it is in I/O mode.
D6=0 & D5=0 as Port 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 83H putting the value of A in 83H which is the port number of the port control register.
- IN 80H 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 81H takes input from 81H which is the port number of port B.
- ADD B add the contents of A register and B register.
- OUT 82H displays the result in 81H which is the port number of port C.
- RET return
- The 8255 is a versatile and widely used programmable peripheral interface that provides 24 input/output pins, allowing for a wide range of input and output operations.
- Using the 8255 allows for easy expansion of the microprocessor’s capabilities by providing additional input/output ports.
- The interface circuit provides an efficient method for performing addition operations by using the add instruction of the 8085 microprocessor and the input/output ports of the 8255.
- The interface circuit is relatively simple and can be easily implemented on a breadboard or printed circuit board.
- The interface circuit requires additional hardware components, such as resistors and capacitors, which may increase the cost and complexity of the overall system.
- The use of the 8255 adds additional overhead to the microprocessor, which may impact the system’s performance.
- The interface circuit may require additional programming to properly configure and control the 8255, which may increase the complexity of the software.
- The interface circuit may not be suitable for all use cases and may require customization to meet specific application requirements.