; File: PCA_2Buf.A51 Date: 03/06/95 ; ; /* (c) Copyright BLUE EARTH RESEARCH, MANKATO, MN 1991-1995 */ ; /* All rights reserved. */ $ ERRORPRINT PAGELENGTH (60) PAGEWIDTH (110) ; Assembler controls $ XREF TITLE (Dual Port Serial Buffer Routine) $ DATE (03/06/95) NOGEN NOMOD51 ; ----------------------------------------------------------------------------- ; 8051 SERIAL INPUT BUFFER ROUTINE ; Written by Tom Bachmann, Blue Earth Research, Mankato, MN 56001 ; Using initial code developed by Tom Hiniker ; ----------------------------------------------------------------------------- ; This program implements a 256 byte circular buffer for receiving serial ; characters via the '51's on-chip UART. It also implements another serial ; buffer for receiving characters on the second serial port. Software for ; transmitting on both the primary and secondary serial port is also ; provided. The equate table can be changed to relocate the buffer and code ; memory to any user desired memory spaces. ; NOTE: Whenever BASIC writes a character to the on-chip UART, it first tests ; the UART's TI bit to determine if the 1 byte transmit buffer is empty or not. ; If the TI bit is "1", indicating the buffer is now empty, BASIC will then ; clear it and load another character into the buffer. Otherwise, it waits ; until it is a "1". Therefore, if another program should clear the TI bit, ; BASIC will go into a wait forever mode when attempting to write to the serial ; port. ; However, for this serial buffer routine to function properly, the TI bit ; must be cleared or the CPU will continuously service the serial interrupt. ; This will make any other program run very slowly since the CPU will only be ; able to execute one instruction between serial interrupts. This program ; therefore clears the TI bit as part of the serial interrupt routine. As a ; result, the BASIC "PRINT" statement may not be used to output characters to ; the serial port once the serial interrupt has been initialized. ; In order to overcome the lack of a useful TI bit, the serial buffer ; program uses a "Sending1" bit that has a similar function. The Sending1 bit ; is set when a character is written to the serial port and cleared by the ; serial interrupt when the TI bit is set by the UART (indicating that the ; character transmission is complete). ; This program provides a CALL to disable the serial interrupt. The serial ; interrupt should be disabled before the BASIC "PRINT" statement is used to ; write characters to the serial port and when BASIC is expected to receive ; serial characters instead of the serial interrupt routine. This should be ; done before executing an INPUT statement or returning to the command mode. ; ----------------------------------------------------------------------------- ; EXAMPLE BASIC LANGUAGE PROGRAM ; ----------------------------------------------------------------------------- ; The following BASIC program was used to test the double buffer program. ; Note that the following jump table is used in the sample BASIC program: ; Address Function ; ------- --------- ; 7E00H Initialize the Serial Interrupt ; 7E02H Check the buffer for characters ; 7E04H Check the 2nd buffer for characters ; 7E06H Transmit a char on the primary port ; 7E08H Transmit a char on the second port ; 7E0AH Disable serial interrupt ; -------------------------- SAMPLE BASIC PROGRAM ----------------------------- ; REM bump up the Stack Pointer to make room for more internal data memory ; 5 DBY(62)=90 ; REM Wait for a while ; 10 FOR X=1 TO 4000 : NEXT X ; REM Initialize serial interrupt ; 20 CALL 7E00H : CHAR=1DH : CHAR2=1AH ; REM Test primary port buffer ; 30 CALL 7E02H : C=DBY(CHAR) : IF C THEN GOSUB 60 ; REM Test the second port buffer ; 40 CALL 7E04H : C=DBY(CHAR2) : IF C=0 THEN 30 ; ; REM Received a character on the secondary buffer: ; REM Echo the character to the primary port ; 50 DBY(CHAR)=C : CALL 7E06H : GOTO 30 ; ; REM Received a character on the primary buffer: ; REM Primary Port: ; REM Output a CR-LF, echo the char, and then another CR-LF ; REM Secondary Port: ; REM Echo the char ; ; 60 GOSUB 80 : DBY(CHAR)=C : CALL 7E06H : GOSUB 80 ; 70 DBY(CHAR2)=C : CALL 7E08H : RETURN ; ; REM Send CR-LF on primary port ; 80 DBY(CHAR)=0DH : CALL 7E06H ; 90 DBY(CHAR)=0AH : CALL 7E06H : RETURN $ EJECT ; ----------------------------------------------------------------------------- ; ASSEMBLY LANGUAGE PROGRAM ; ----------------------------------------------------------------------------- ; For each serial character received, the Buffer "Head" address pointer is ; bumped and the received character stored into that location. Reading the ; buffer is accomplished by bumping the Buffer "Tail" address pointer and then ; reading that location into "Char" so BASIC can get it using a simple DBY() ; instruction. If the Head & Tail pointers are equal, then the Buffer is ; considered empty. Trying to read an empty Buffer will produce a NULL code ; (0) in Char and will not advance the Tail pointer. A BASIC program can just ; check for a 0 in Char if it does not want to check Head & Tail pointers ; before doing a "ReadBuffer". ; Note that the above is true for BOTH the primary and secondary serial ; ports. The primary port uses the Head, Tail, and Char memory locations, ; while the secondary port uses the Head2, Tail2, and Char2 memory locations. ; 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� ; � SYMBOL DEFINITIONS � ; 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� $ NOLIST ; DON'T SHOW IN LIST FILE $ INCLUDE(REGFX.INC) ; INCLUDE 83C51FB REGISTERS $ LIST ; SHOW THE REST IN THE LIST FILE ; ----------------------------- EQUATE TABLE ---------------------------------- Buffer XDATA 5000H ; Where circular Buffer starts DSEG AT 1AH Char2: DS 1 ; Contains retrieved character Tail2: DS 1 ; Pointer to last character read Head2: DS 1 ; Pointer to last character stuffed Buffer2 XDATA 5100H ; Repeat for 2nd Serial Port Char: DS 1 Tail: DS 1 Head: DS 1 CodeAddr CODE 7E00H ; Locate this program at top of ; write protectable memory space ; --------------------- SECOND SERIAL PORT EQUATE TABLE ----------------------- DSEG AT 4DH BitCounter: DS 1 ; Counter for receiving bits RecvTemp: DS 1 ; Software Receive SBUF TxmCounter: DS 1 ; Counter for sending bits TxmTemp: DS 1 ; Software Transmit SBUF LoHalfBitTime: DS 1 ; Hold the reload values for the HiHalfBitTime: DS 1 ; PCA Serial Port Timing LoFullBitTime: DS 1 ; Hold the reload values for the HiFullBitTime: DS 1 ; PCA Serial Port Timing BSEG AT 0 StartBit: DBIT 1 ; Receive Flags DoneBit: DBIT 1 TxmStart: DBIT 1 ; Transmit Bits InProgress: DBIT 1 Sending1: DBIT 1 ; Primary port "InProgress" bit NegEdge EQU 011H SoftTimer EQU 049H ; NOTE: The serial port Baud Rate can be changed by editing the following ; program variable and then assembling the source file. Baud EQU 96 ; Baud Rate in 00's (9600) FullBitTime EQU 10000/Baud ; 417uS is the bit period HalfBitTime EQU FullBitTime/2 ; for 2400 baud. (12 Mhz) ; Also note that the baud rate reload values are held in internal memory ; locations so that they may be changed at any time by the calling program. $ EJECT ; ------------------------ BEGINNING OF EXECUTABLE CODE ----------------------- CSEG AT CodeAddr AJMP StartSerial ; 7E00H Initialize the Serial Interrupt AJMP ReadBuffer ; 7E02H Check the buffer for characters AJMP ReadBuffer2 ; 7E04H Check the 2nd buffer for characters AJMP WriteChar ; 7E06H Transmit a char on the primary port AJMP WriteChar2 ; 7E08H Transmit a char on the second port ; ------------------------- DISABLE SERIAL INTERRUPT -------------------------- ; May want to load SBUF with 1st character of an output string instead of a ; NULL and let BASIC take care of sending the rest of them. StopSerial: CLR ES ; 7E0AH Disable serial interrupt WriteCR: MOV SBUF,#0DH ; Write to set TI bit RET WriteChar: JB Sending1,$ ; Wait if previous char is not gone. MOV SBUF,Char SETB Sending1 RET ; ---------------------- SERIAL INTERRUPT ROUTINE ----------------------------- SerialInt: JBC TI,TxDInt ; Not a receive interrupt ? PUSH PSW ; Save registers PUSH ACC PUSH DPH PUSH DPL INC Head MOV DPH,#HIGH Buffer ; Page pointer always the same. MOV DPL,Head MOV A,SBUF ; Get serial input character CLR RI ; and reenable interrupt. MOVX @DPTR,A ; Store character in Buffer POP DPL ; Restore registers POP DPH POP ACC POP PSW RETI TxDInt: CLR Sending1 ; Done with primary port character. RETI ; ---------------------- READ CHARACTER FROM BUFFER --------------------------- ReadBuffer: MOV A,Head ; If Head & Tail are the same, XRL A,Tail ; the Buffer is considered empty. JNZ GetChar MOV Char,A ; So return with NULL character RET GetChar: INC Tail MOV DPH,#HIGH Buffer MOV DPL,Tail MOVX A,@DPTR ; Read the Buffer MOV Char,A ; and put it here. RET ; ---------------------- READ CHARACTER FROM BUFFER2 -------------------------- ReadBuffer2: MOV A,Head2 ; If Head & Tail are the same, XRL A,Tail2 ; the Buffer is considered empty. JNZ GetChar2 MOV Char2,A ; So return with NULL character RET GetChar2: INC Tail2 MOV DPH,#HIGH Buffer2 MOV DPL,Tail2 MOVX A,@DPTR ; Read the Buffer MOV Char2,A ; and put it here. RET ; ------------------------INITIALIZE SERIAL INTERRUPT ------------------------- StartSerial: MOV DPTR,#4023H ; Write LJMP code to serial MOV A,#2 ; interrupt vector location. MOVX @DPTR,A INC DPTR MOV A,#HIGH SerialInt MOVX @DPTR,A INC DPTR MOV A,#LOW SerialInt MOVX @DPTR,A MOV DPTR,#4033H ; Stuff "LJMP PCAINT" into MOV A,#2 ; mirrored PCA interrupt MOVX @DPTR,A ; vector at address 4033H. INC DPTR MOV A,#HIGH PCAINT ; Location of PCA MOVX @DPTR,A ; interrupt routine. INC DPTR MOV A,#LOW PCAINT MOVX @DPTR,A ; Now initialize Head and Tail pointers so that the first byte received is ; stored in (and read from) location 0 (the pointers are incremented BEFORE ; the byte is stored or read). TMB 9/23/92 MOV Head,#0FFH ; Initialize Buffer pointers MOV Tail,#0FFH MOV Char,#0 ; Initialize Char to "NULL" MOV Head2,#0FFH ; Initialize Buffer pointers MOV Tail2,#0FFH MOV Char2,#0 ; Initialize Char to "NULL" ; Keep the baud rate reload values in internal memory so that they ; can be changed at any time by the system software. MOV LoHalfBitTime, #LOW HalfBitTime MOV HiHalfBitTime, #HIGH HalfBitTime MOV LoFullBitTime, #LOW FullBitTime MOV HiFullBitTime, #High FullBitTime CLR Sending1 ; Primary port ready for characters ; 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� ; � INITIALIZE RECEIVE MODE � ; 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� CLR StartBit CLR DoneBit MOV RecvTemp,#0 ; 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� ; � INITIALIZE TRANSMIT MODE � ; 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� CLR TxmStart CLR InProgress MOV TxmTemp,#0 $ EJECT ; 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� ; � INITIALIZE CPU FUNCTIONS � ; 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� MOV CL,#0 ; CLEAR PCA TIMER REGISTERS MOV CH,#0 ; 旼컴컴컫컴컴컴쩡컴컴컫컴컴컴쩡컴컴컫컴컴컴쩡컴컴컫컴컴컴� ; CCAPM = � -- � ECOM � CAPP � CAPN � MAT � TOG � PWM � ECCF � ; 읕컴컴컨컴컴컴좔컴컴컨컴컴컴좔컴컴컨컴컴컴좔컴컴컨컴컴컴� ; Module 3 -> Capture Negative edge w/interrupt ; 0 0 0 1 0 0 0 1 ; Module 4 -> Software Timer for serial port ; 0 1 0 0 1 0 0 1 MOV CCAPM3,#NegEdge ; MOV CCAPM4,#SoftTimer ; NOT YET! MOV CCAPM4,#0 ; 旼컴컴컫컴컴컴쩡컴컴컫컴컴컴쩡컴컴컫컴컴컴쩡컴컴컫컴컴컴� ; CMOD = � CIDL � WDTE � -- � -- � -- � CPS1 � CPS0 � ECF � ; 읕컴컴컨컴컴컴좔컴컴컨컴컴컴좔컴컴컨컴컴컴좔컴컴컨컴컴컴� ; 0 0 0 0 0 0 0 0 MOV CMOD,#0 ; 旼컴컴컫컴컴컴쩡컴컴컫컴컴컴쩡컴컴컫컴컴컴쩡컴컴컫컴컴컴� ; CCON = � CF � CR � -- � CCF4 � CCF3 � CCF2 � CCF1 � CCF0 � ; 읕컴컴컨컴컴컴좔컴컴컨컴컴컴좔컴컴컨컴컴컴좔컴컴컨컴컴컴� ; 0 1 0 0 0 0 0 0 MOV CCON,#40H ; 旼컴컴컫컴컴컴쩡컴컴컫컴컴컴쩡컴컴컫컴컴컴쩡컴컴컫컴컴컴� ; IE = � EA � EC � ET2 � ES � ET1 � EX1 � ET0 � EX0 � ; 읕컴컴컨컴컴컴좔컴컴컨컴컴컴좔컴컴컨컴컴컴좔컴컴컨컴컴컴� ; 1 1 0 1 0 0 0 0 SETB EC SETB ES SETB EA RET $ EJECT ; 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� ; � SET UP TO TRANSMIT A CHARACTER � ; 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� WriteChar2: PUSH PSW JB InProgress,$ ; Make sure no previous chars yet CLR TxmStart ; Clear status flag MOV TxmTemp,Char2 ; Load "SBUF" with data byte MOV TxmCounter,#9 ; 8 data bits + 1 stop bit MOV A,LoFullBitTime ; Setup for the next PCA interrupt ADD A,CL MOV CCAP4L,A MOV A,HiFullBitTime ADDC A,CH MOV CCAP4H,A CLR CCF4 ; Get rid of any old flags MOV CCAPM4,#SoftTimer ; Start the PCA timer compare SETB InProgress POP PSW RET ; End of function call ; 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� ; � PCA INTERRUPT � ; 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� PCAINT: JBC CCF3,ReceiveInt ; Check for receive Interrupt JNB CCF4,NoMore ; Not a valid Interrupt ; ---------------------------- TRANSMIT INTERRUPT ----------------------------- TransmitInt: CLR CCF4 PUSH ACC PUSH PSW JNB InProgress,TxmDone JB TxmStart,SendByte ; See if Start Bit was sent CLR P1.7 ; Otherwise transmit Start bit SETB TxmStart ; Set start bit flag SJMP TxmDone SendByte: DJNZ TxmCounter,TxmNext ; Transmit 8 data bits TxmStop: SETB P1.7 ; Transmit stop bit CLR InProgress ; Transmission Completed! MOV CCAPM4,#0 ; Turn the PCA timer module off SJMP Txm_End TxmNext: MOV A,TxmTemp ; Transmit one bit at a time RRC A ; through the carry bit MOV P1.7,C MOV TxmTemp,A ; Save for next time TxmDone: MOV A,LoFullBitTime ; Setup for next PCA int. ADD A,CCAP4L MOV CCAP4L,A MOV A,HiFullBitTime ADDC A,CCAP4H MOV CCAP4H,A Txm_End: JBC CCF3,ReceiveNow ; Also Check for receive POP PSW POP ACC NoMore: RETI ; ---------------------------- RECEIVE INTERRUPT ------------------------------ ReceiveInt: PUSH ACC PUSH PSW ReceiveNow: MOV A,CCAPM3 ANL A,#7FH CJNE A,#NegEdge,CheckStart MOV A,LoHalfBitTime ; Setup for next PCA int. ADD A,CCAP3L MOV CCAP3L,A MOV A,HiHalfBitTime ADDC A,CCAP3H MOV CCAP3H,A MOV CCAPM3,#SoftTimer POP PSW POP ACC RETI CheckStart: CJNE A,#SoftTimer,Error JB StartBit,DecrBitCtr JB P1.6,Error SETB StartBit MOV BitCounter,#9 SetUpFull: MOV A,LoFullBitTime ; Setup for next PCA int. ADD A,CCAP3L MOV CCAP3L,A MOV A,HiFullBitTime ADDC A,CCAP3H MOV CCAP3H,A POP PSW POP ACC RETI DecrBitCtr: DJNZ BitCounter,RotateBit CheckStop: JNB P1.6,Error CLR StartBit MOV CCAPM3,#NegEdge SETB DoneBit ; Got the character! PUSH DPH ; Save DPTR PUSH DPL INC Head2 ; Increment buffer pointer MOV DPH,#HIGH Buffer2 ; Store received character MOV DPL,Head2 ; in next buffer location. MOV A,RecvTemp MOVX @DPTR,A POP DPL POP DPH ; Restore DPTR POP PSW POP ACC RETI RotateBit: MOV C,P1.6 ; Shift in next data bit. MOV A,RecvTemp RRC A MOV RecvTemp,A SJMP SetUpFull Error: MOV CCAPM3,#NegEdge ; Receive error. CLR StartBit POP PSW POP ACC RETI END ; Following is the HEX file derived from the assembled source ; file. This can be used for directly loading the program via ; MONITOR-51 and almost any terminal program. :107E0000C167C13DC152C110C1CAC2AC75990D2232 :107E10002004FD851D99D2042210991EC0D0C0E017 :107E2000C083C082051F758350851F82E599C29863 :107E3000F0D082D083D0E0D0D032C20432E51F65CA :107E40001E7003F51D22051E758350851E82E0F508 :107E50001D22E51C651B7003F51A22051B75835155 :107E6000851B82E0F51A229040237402F0A3747EF1 :107E7000F0A37419F09040337402F0A3747EF0A361 :107E800074EDF0751FFF751EFF751D00751CFF75E5 :107E90001BFF751A0075513475520075536875547F :107EA00000C204C200C201754E00C202C203755076 :107EB0000075E90075F90075DD1175DE0075D900F2 :107EC00075D840D2AED2ACD2AF22C0D02003FDC212 :107ED00002851A50754F09E55325E9F5EEE554354D :107EE000F9F5FEC2DC75DE49D203D0D02210DB3CAE :107EF00030DC38C2DCC0E0C0D030031C200206C237 :107F000097D2028013D54F09D297C20375DE008045 :107F100013E550139297F550E55325EEF5EEE55431 :107F200035FEF5FE10DB09D0D0D0E032C0E0C0D085 :107F3000E5DD547FB41114E55125EDF5EDE552353D :107F4000FDF5FD75DD49D0D0D0E032B4494A2000BE :107F500019209644D200754D09E55325EDF5EDE560 :107F60005435FDF5FDD0D0D0E032D54D22309628E5 :107F7000C20075DD11D201C083C082051C7583511A :107F8000851C82E54EF0D082D083D0D0D0E032A2E2 :107F900096E54E13F54E80C175DD11C200D0D0D0EC :027FA000E032CD :00000001FF