Using the 8051 Serial Port and Interrupts The purpose of this lab is to control

Question

Using the 8051 Serial Port and Interrupts

The purpose of this lab is to control and program the serial port of the micro-controller in a given sequence. Two switches SW1 and SW2are are connected to the micro-controller input port bits P1.1 and P1.2. The two switches define the required Baud rate requirements for the serial communication as follows:

SW1

SW2

Baud (bps)

0

0

1200

0

1

2400

1

0

4800

1

1

9600

Steps

First, write a subroutine ”BCODE” (Baud Code) starting at code address 200H to detect the setting of SW1 and SW2 and return a value in accumulator B (0 for 1200, 1 for 2400, 2 for 4800, and 3 for 9600 Baud. It also setup the TH1 register for the requested BAUD rate.

Second, write a subroutine “CONFIG” (Timers, Interrupts, and Serial Configuration) starting at code address 300H to configure the serial port for Mode 1, timer 0 for mode 1, and timer 1 for mode 2. Also it enables the timer 0 interrupt and start timer 0 and timer 1.

.

Third, write a subroutine “SDISPLAY”” (Serial Display) starting at code starting address of 400H to display on the serial port the message “SERIAL BAUD IS XXXX BPS”. “XXXX” is the actual Baud rate value. The subroutine will use polling on the TI flag.

Fourth, write a Timer 0 Interrupt Service Routine “TIMER0H” at address 500H to provide maximum delay in updating port 3 based on the status of input port 2..

Test and debug your program. Also document and submit your final report along with the well documented list file. Monitor the serial port window and verify the SBUF contents using the ASCII code for the selected message and associated BAUD rate. You can slow the SBUF update by controlling the MC clock using the clock window in the PREPHERALS selection. Make sure to check the “4x” box.

Modify the program in order to perform serial character transmission using the serial port interrupt instead of the use of polling on the TI flag. The processor will be reading Port 2 (P2) and outputting the input byte to Port 3 (P3) while the serial message is being transmitted.

Document the new program and explain how the interrupt structure worked for Timer 0 and the Serial Port.

SW1

SW2

Baud (bps)

0

0

1200

0

1

2400

1

0

4800

1

1

9600

Explanation / Answer

in 8051 micro controller p3 port supports communication in case you are using input any other port rest of p3 programming like this using timer / counters observe the code once

sw1 equ p1.0
org 0h
main:   mov tmod,#20h
        mov th1,#-3 % mention the baud rate of 8051 microcontroller
        mov scon,#50h
        setb tr1
        setb sw1
sb1:    jb sw1,next
        mov dptr,#mess1
fn:     clr a
        movc a,@a+dptr
        jz sb1
        acall sendcom
        inc dptr
        sjmp fn
next:   mov dptr,#mess2
ln:     clr a
        movc a,@a+dptr
        jz sb1
        acall sendcom
        inc dptr
        sjmp ln
sendcom:mov sbuf,a
here:   jnb ti,here
        clr ti
        ret
mess2: db "chegg",0
mess1: db "expert ",0
end

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