PIC的RS232通訊程序

;*************************************************************
?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+6
redo??? decfsz? DlyCnt,Same
?goto??? redo
?retlw?? 0
;
Delay1? movwf?? DlyCnt
redo_1? decfsz? DlyCnt,Same???? ;
?goto??? redo_1
?goto??? User
;
Delay2? movwf?? DlyCnt
redo_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_X1
R0_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??? cycle4
cycle4? 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_1
Sync_2? goto??? User
;
;****************************************************************
;
Shell?? btfsc?? FlagRX,R_flag
?goto??? Chek_X
?btfsc?? FlagRX,X_flag
?goto??? R0_X1
?goto??? R0_X0??????????? ; Case for R0_X0
Chek_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??? ErrChk
SetXmt? 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??? SetXmt
error?? goto??? error?????????? ; Received word is not "Z"
;
Op????? btfss?? RTCC,MSB??????? ; Test for RTCC bit 7
?goto??? Op????????????? ; If Set, Then RTCC has incremented
Oflow?? goto??? Op_Sys????????? ; to 128.
;
; ***********************************************************
;
?ORG???? PIC54
?goto??? main

?END