PIC的RS232通讯程序（RS232编程）

PIC的RS232通讯程序（RS232编程）

PIC的RS232通讯程序

;************************************************************* TITLE   "RS232 CommunicaTIon Using PIC16C54";;    Comments :;               (1) Full Duplex;               (2) Tested from 1200 to 9600 Baud( @ 8 Mhz );               (3) Tested from 1200 to 19200 Baud(@ 16 & 20 Mhz);;       The User gets a total TIme as specified by the User Cycles;       in the table ( or from equaTIons ). The user routine has to;       exactly use up this amount of time. After this time the User;       routine has to give up the control to the Operating System.;       If less than 52 uS is used, then the user should wait in a;       delay loop, until exactly 52 uS.;;       Transmission :;               Transmit Data is output on DX pin (Bit DX of Port_A).;               In the user routine, the user should load the;               data to be transmitted in the XmtReg and Set the;               X_flag ( bsf FlagRX,X_flag ). This flag gets cleared;               after the transmission.;;       Reception :;               Data is received on pin DR ( bit DR of Port_A ).;               The User should constantly check the "R_done" flag;               to see if reception is over. If the reception is;               in progress, R_flag is set to 1.;               If the reception is over, "R_done" flag is set to 1.;               The "R_done" flag gets reset to zero when a next start;               bit is detected. So, the user should constantly check;               the R_done flag, and if SET, then the received word;               is in Register "RcvReg". This register gets cleared;               when a new start bit is detected.;;    Program Memory :;       Total Program Memory Locations Used ( except initialization;       in "main" & User routine ) = 132 locations.;;    Data Memory :;       Total Data memory locations (file registers used) = 6;               2 File registers to hold Xmt Data & Rcv Data;               1 File registers for Xmt/Rcv flag test bits;               3 File registers for delay count & scratch pad;;    Stack :;       Only one level of stack is used in the Operating System/RS232;       routine. But this is freed as soon as the program returns to the;       user routine.;;    RTCC :     Not Used;    WDT  :     Not Used; INCLUDE         "PICREG.H" INCLUDE         "RS232.H"; ORG     0;**************************************************************;Delay   movlw   K0+1 movwf   DlyCnt          ; Total Delay = 3K+6redo    decfsz  DlyCnt,Same goto    redo retlw   0;Delay1  movwf   DlyCntredo_1  decfsz  DlyCnt,Same     ; goto    redo_1 goto    User;Delay2  movwf   DlyCntredo_2  decfsz  DlyCnt,Same     ; Delay =   = 260 Cycles goto    redo_2 goto    User_1;R_strt  btfsc   Port_A,DR       ; check for a Start Bit goto    ShellY          ; delay for 104/2 uS bcf     FlagRX,R_done   ; Reset Receive done flag bsf     FlagRX,R_flag   ; Set flag for Reception in Progress btfss   FlagRX,BitXsb bsf     FlagRX,A_flag   ; A_flag is for start bit detected in R_strt clrf    RcvReg          ; Clear all bits of RcvReg IF      R_Nbit movlw   8               ; 8 Data bits ELSE movlw   7               ; 7 data bits ENDIF movwf   Rcount goto    Shell           ; delay for 104+104/4;ShellY  btfss   FlagRX,BitXsb goto    Shell bsf     FlagRX,R_flag goto    Shell;R_next  bcf     STATUS,CARRY IF      R_MODE rrf     RcvReg,Same     ; to set if MSB first or LSB first ELSE rlf     RcvReg,Same ENDIF btfsc   Port_A,DR IF      R_MODE   IF      R_Nbit   bsf     RcvReg,MSB       ; Conditional Assembly   ELSE   bsf     RcvReg,MSB-1   ENDIF ELSE bsf     RcvReg,LSB ENDIF decfsz  Rcount,Same goto    Shell bcf     FlagRX,R_flag bsf     FlagRX,S_flag bsf     FlagRX,R_done goto    Shell;;       Reception Done;X_strt  bcf     Port_A,DX       ; Send Start Bit IF      X_Nbit movlw   8 ELSE movlw   7 ENDIF movwf   Xcount IF      X_MODE ELSE   IF    X_Nbit   ELSE   rlf   XmtReg,Same   ENDIF ENDIF goto    X_SB;X_next  bcf     STATUS,CARRY IF      X_MODE rrf     XmtReg,Same     ; Conditional Assembly ELSE                    ; to set if MSB first or LSB first rlf     XmtReg,Same ENDIF btfsc   STATUS,CARRY bsf     Port_A,DX btfss   STATUS,CARRY bcf     Port_A,DX decf    Xcount,Same goto    X_Data;X_SB_1  bcf     FlagRX,X_flag   ; Xmt flag = 0 -- transmission over movlw   9 movwf   Xcount bsf     Port_A,DX       ; Send Stop Bit goto    X_Stop;X_SB_2  bsf     Port_A,DX bcf     FlagRX,S_bit goto    X_Stop;;   End of Transmission;R0_X0   btfss   FlagRX,S_flag goto    User bcf     FlagRX,S_flag call    Delay movlw   K7+1 goto    Delay1;R1_X0 call    Delay movlw   K1+1            ; delay for 1st bit is 104+104/4 movwf   DlyCnt IF      R_Nbit movlw   8               ; 8 Data bits ELSE movlw   7               ; 7 data bits ENDIF xorwf   Rcount,W btfsc   STATUS,Z_bit goto    redo_1 movlw   K2+1 goto    Delay1;R1_X1                           ; same as R0_X1R0_X1   movlw   9 subwf   Xcount,W btfsc   STATUS,Z_bit goto    X_strt movf    Xcount,Same     ; to check if All data bits Xmted btfss   STATUS,Z_bit goto    X_next IF      SB2   btfsc FlagRX,S_bit   goto  X_SB_2   bsf   FlagRX,S_bit   goto  X_SB_1 ELSE   goto    X_SB_1 ENDIF;;X_SB    goto    cycle4cycle4  goto    X_Data;X_Data  btfsc   FlagRX,A_flag goto    SbDly btfsc   FlagRX,BitXsb goto    ABC call    Delay movlw   K3+1 goto    Delay2;SbDly   bcf     FlagRX,A_flag call    Delay movlw   K4+1 goto    Delay2;ABC     bcf     FlagRX,BitXsb call    Delay goto    User_1;X_Stop btfsc   FlagRX,A_flag goto    SbDly btfsc   FlagRX,BitXsb goto    ABC call    Delay movlw   K5+1 goto    Delay2;User_1  btfsc   FlagRX,R_flag goto    Sync_1          ; Reception already in progress btfsc   FlagRX,S_flag goto    Sync_3 btfsc   Port_A,DR       ; check for a Start Bit goto    Sync_2          ; No Start Bit - goto User routine bcf     FlagRX,R_done   ; Reset Receive done flag bcf     FlagRX,R_flag bsf     FlagRX,BitXsb   ; Set flag for Reception in Progress clrf    RcvReg          ; Clear all bits of RcvReg IF      R_Nbit movlw   8               ; 8 Data bits ELSE movlw   7               ; 7 data bits ENDIF movwf   Rcount goto    User;Sync_3  bcf     FlagRX,S_flag movlw   K6+1 goto    Delay1;Sync_1Sync_2  goto    User;;****************************************************************;Shell   btfsc   FlagRX,R_flag goto    Chek_X btfsc   FlagRX,X_flag goto    R0_X1 goto    R0_X0            ; Case for R0_X0Chek_X  btfsc   FlagRX,X_flag goto    R1_X1 goto    R1_X0;;;****************************************************************;       Operating System;  The User routine after time = B/2, should branch Here;Op_Sys  btfss   FlagRX,R_flag goto    R_strt goto    R_next;;***************************************************************;main    movlw   0EH             ; Bit 0 of Port A is Output tris    Port_A          ; Set Port_A.0 as output ( DX );                                 & Port_A.1 is input ( DR ) bsf     Port_A,DX movlw   9 movwf   Xcount          ; If Xcount == 9, Then send start bit clrf    FlagRX          ; Clear All flag bits. IF      SB2   bsf     FlagRX,S_bit    ; Set Xmt Stop bit flag(2 Stop Bits) ELSE   bcf     FlagRX,S_bit    ; Clear Xmt Stop bit flag ENDIF movlw   1FH               ; Prescaler = 4 OPTION                    ; Set RTCC increment on internal Clock goto    Op_Sys;;***********************************************************;;       *******************  User Routine  ***************;  The User routine should use up time exactly = User time as given;  in the Constants Table ( or by Equations for constants ).;  At 9600, this 86 Clock Cycles. RTCC timer is used here to count;  upto 86 cycles ( From 128-86 To 0 ) by examining Bit 7 of RTCC.;K_user  equ     .128+.6-.86;User    movlw   K_user movwf   RTCC btfsc   FlagRX,R_done goto    ErrChkSetXmt  btfsc   FlagRX,X_flag goto    Op movlw   41H movwf   XmtReg bsf     FlagRX,X_flag   ; Enable Xmission goto    Op;ErrChk movlw   "Z" xorwf   RcvReg,W btfsc   STATUS,Z_bit goto    SetXmterror   goto    error           ; Received word is not "Z";Op      btfss   RTCC,MSB        ; Test for RTCC bit 7 goto    Op              ; If Set, Then RTCC has incrementedOflow   goto    Op_Sys          ; to 128.;; ***********************************************************; ORG     PIC54 goto    main

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