Write an 8086 assembly language program to accomplish this

Question

An 8086-8255 based system is required to operate an 7-segment display (Common-Cathode) connected to Port A based on two switch inputs connected to bit 0 and 1 of Port B as Fig.B. If both switches are either high or low, display number 0; otherwise, display number 1. Assume base address of 60H. Write an 8086 assembly language program to accomplish this.

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Answer 1

Hey Mohin! Here's an 8086 assembly language program that uses an 8255 interface to control a 7-segment display based on the states of two switches connected to Port B. The program checks the inputs on Port B and displays either 0 or 1 on the 7-segment display connected to Port A.

Assumptions

1. Base address of the 8255 is 60H.
2. The 7-segment display encodes the digits as follows:
3. 0: 3FH (binary: 00111111)
4. 1: 06H (binary: 00000110)

Assembly Program

; Define base address for 8255

BASE_ADDR EQU 60H

PORT_A EQU BASE_ADDR ; Port A address

PORT_B EQU BASE_ADDR + 1 ; Port B address

CONTROL_PORT EQU BASE_ADDR + 2 ; Control Port address

; Define constants for display

ZERO EQU 3FH ; Display value for 0

ONE EQU 06H ; Display value for 1

ORG 100H ; Set origin for COM file

START:

; Initialize 8255

MOV AL, 80H ; Set Port A and B as output, Control Port as input

OUT CONTROL_PORT, AL ; Send configuration to control register

MAIN_LOOP:

; Read switches from Port B

IN AL, PORT_B ; Read from Port B

; Check the status of the switches

AND AL, 03H ; Mask to get only the first two bits

CMP AL, 00H ; Check if both switches are low

JE DISPLAY_ZERO ; Jump to DISPLAY_ZERO if both are low

CMP AL, 03H ; Check if both switches are high

JE DISPLAY_ZERO ; Jump to DISPLAY_ZERO if both are high

; If switches are not the same, display 1

MOV AL, ONE ; Load value for 1

JMP DISPLAY

DISPLAY_ZERO:

MOV AL, ZERO ; Load value for 0

DISPLAY:

; Send value to Port A to display on the 7-segment

OUT PORT_A, AL ; Output the value to Port A

; Loop back

JMP MAIN_LOOP ; Repeat the process

END:

HLT ; Halt the CPU

Explanation

1. Initialization: The 8255 is initialized by sending a configuration to the control port to set Port A as an output and Port B as an input.
2. Main Loop: The program enters a loop where it continuously reads the state of the switches from Port B.
3. Switch Checking:
4. The input from Port B is masked to isolate the first two bits, which correspond to the switch inputs.
5. If both switches are either high or low, the program prepares to display 0.
6. If the switches are different, the program prepares to display 1.
7. Display Output: The appropriate value (0 or 1) is sent to Port A to control the 7-segment display.
8. Loop: The program loops back to read the switch inputs continuously.

Make sure to set up your 8255 and 7-segment display correctly according to the hardware specifications and connections. This program assumes a basic configuration with the necessary addresses.

I'll be glad to help you in further tutoring sessions!

Best,

Andrew