m3t2.asm

用于51系列单片机的串口程序源码

;FILE: M3T2.ASM
;
;THIS PROGRAM TRANSMITS THE HEX VALUE AA REPETITIVELY ACCROSS THE SERIAL PORT
;OF A MCS-51 IN MODE 3 USING TIMER 2 AS A BAUD RATE GENERATOR TO
;GENERATE A BAUD RATE OF 2400 BAUD AT 16MHZ WITH A PARITY BIT
;
;DETAILS:
;
;MODE 3:  11 BITS ARE TRANSMITTED THROUGH TXD OR RECEIVED THROUGH RXD
;TRANSMISSION STARTS WITH A START BIT (0), EIGHT DATA BITS WITH THE LEAST 
;SIGNIFICANT BIT FIRST, A PROGRAMMABLE 9TH DATA BIT, AND A STOP BIT (1).  
;MODE 3 IS THE SAME AS MODE 2 EXCEPT THAT MODE 3 HAS A VARIABLE
;BAUD RATE
;
;
        RCAP2H EQU 0CBH
        RCAP2L EQU 0CAH
        T2CON  EQU 0C8H

        ORG 00H
        JMP MAIN
MAIN:   MOV SCON,#0C0H      ;SET UP FOR SERIAL MODE 3
        MOV RCAP2H,#0FFH    ;LOAD HIGH BYTE TO GENERATE 2400 BAUD AT 16MHZ
        MOV RCAP2L,#30H     ;LOAD LOW BYTE TO GENERATE 2400 BAUD AT 16MHZ
        MOV T2CON,#14       ;TIMER 2 BAUD RATE GENERATOR AND START TIMER
        MOV A,#0AAH         ;PUT THE VALUE TO BE TRANSMITTED IN THE ACC
        MOV C,P             ;PARITY INFORMATION TO CARRY FLAG
        MOV TB8,C           ;PARITY INFO FROM CARRY TO PROGRAMABLE BIT *
;                            *NOTE: THE CONTENTS OF THE CARRY FLAG IN THE 
;                                   PSW MAY BE ALTERED
        CLR TI              ;READY TO TRANSMIT
LOOP:   MOV SBUF,A          ;TRANSMIT AAH
        JNB TI,$            ;WAIT UNTIL DONE TRANSMITING
        CLR TI              ;READY TO TRANSMIT
        JMP LOOP            ;DO IT ALL OVER AGAIN
        END