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; ; Interrupt based USART1 routines ; ; John E. Andrews ; Feb 24th, 1998 ; ;********************************************************************** InitU1 ; initialize USART1 ;********************************************************************** ; ; This sets up the peripheral USART1 to provide buffered, line based, ; interrupt driven, transmit and receive. The functions UART1Rx and ; UART1Tx are called from the peripheral interrupt vector. ; These functions are terminated by a return to the peripheral isr ; which restores context and performs the retfie. ; This function, InitU1, and the routine to start interrupt based ; buffer transission, StartTx are called by inline code. ; ; ***** Variable and symbol declarations for UART1 ***** ; cblock ; declare bank 0 variables u1Flags ; UART1 semaphore flags endc ; ; bit flag definitions for u1Flags RxRdy equ 0 ; new data from UART1 for inline code RstRxPtr equ 1 ; isr should reset its buffer pointer TxRdy equ 2 ; new data for UART1 from inline code ; ; select gpr bank containing Rx buffer, pointers and flags movlr 0 ; select gpr bank 0 movlw rxBuffer-1 ; load prestart of Rx buffer movwf rxPtr ; into Rx buffer pointer clrf u1Flags ; clear all semaphors bsf u1Flags, RstRxPtr ; tell isr to reset Rx pointer bcf u1Flags, RxRdy ; clear data ready flag ; ; init peripheral movlb 0 ; select SFR bank for USART1 movlw 0x20 ; select TxEN, 8 bit, asynch movwf TXSTA1 ; for USART1 Tx movlw 0x90 ; select SPEN, RxEN, continuous Rx movwf RCSTA1 ; for USART1 Rx movlw (Dev_Freq/(64*9600))-1 ; select 9600 movwf SPBRG1 ; for USART1 baud rate ; ; init interupts for USART1 movlb 1 ; select sfr bank 1 bsf PIE1, RC1IE ; enable Rx int return ; ;********************************************************************** UART1Rx ; UART1 receiver interrupt service routine ;********************************************************************** ; ; Receive characters into buffer until CR is received. Then set ; RxRdy bit in u1Flags register to inform inline code that a line ; is ready. Once the inline code has finished with the buffer it sets ; RstRxPtr to cause the isr buffer pointer, intRxPtr, to be set equal ; to the inline code buffer pointer, rxPtr, it then clears RxRdy ; allowing the isr to reset and begin accumulating a new buffer. ; ; This function ; must be terminated by a return to the peripheral isr which restores ; context and performs the retfie. ; ; The following macro causes this function to be called by the ; peripheral interrupt routine when the RC1IF flag is set. This macro ; must be placed immediately following the label at the beginning of ; the isr function and prior to any executable code. ; ; include bit testing at the peripheral int vector at assembly time InstallISR 1, PIR1, RC1IF ; install isr for uart1 rx ; ; ***** Variable and symbol declarations for UART1 Rx isr ***** ; rxBufferSize equ 40 ; size of buffer for UART1 Rx data ; cblock ; declare bank 0 variables ; UART1 Rx buffer, allow extra char for 0 fil by command parser rxBuffer: rxBufferSize+1 rxPtr ; pointer into Rx buffer used by inline code intRxPtr ; pointer into Rx buffer used by isr endc ; ; ***** Executable code for USRT1 Rx isr ***** ; ; select gpr bank containing Rx buffer, pointers and flags movlr 0 ; select gpr bank 0 ; select sfr bank containing UART1 registers movlb 0 ; select sfr bank 0 ; ; if buffer has data ready then read Rx data into bit bucket btfss u1Flags, RxRdy ; skip if buffer has whole line ready goto RstRx ; otherwise test for buffer reset movfp RCREG1, WREG ; read Rx data into bit bucket return ; return to restore context and exit isr ; RstRx ; reset isr uart Rx buffer pointer to equal inline code pointer btfss u1Flags, RstRxPtr ; skip if reset requested goto ReadRx ; otherwise continue to buffer Rx data movfp rxPtr, WREG ; fetch inline buffer ptr movwf intRxPtr ; reset isr Rx pointer bcf u1Flags, RstRxPtr ; clear pointer rst flag ; ReadRx ; point to next buffer entry and copy in Rx character incf intRxPtr ; inc isr Rx pointer movfp intRxPtr, FSR0 ; load FSR0 movfp RCREG1, INDF0 ; read Rx data into buffer ; ; process special characters ; ; if a LF was received echo it then throw it away movlw 0x0A ; test for LF cpfseq INDF0 ; if equal then skip goto RxNotLF ; otherwise jump to not LF movpf INDF0, TXREG1 ; echo it back to the term decf intRxPtr ; backup isr pointer deleting LF return ; return to restore context and exit isr RxNotLF ; if here then character was not LF ; ; if a backspace was received then backup movlw 0x08 ; test for backspace cpfseq INDF0 ; if equal skip goto RxNotBS ; otherwise jump to not BS decf intRxPtr ; backup over backspace char ; this prevents backing up past the beginning of the buffer movlw rxBuffer-1 ; load prestart of Rx buffer cpfsgt intRxPtr ; skip if current pointer greater return ; return to restore context and exit isr decf intRxPtr ; otherwise backup over prior char movpf INDF0, TXREG1 ; and echo it back to the term return ; return to restore context and exit isr RxNotBS ; if here then character was not backspace ; ; if a CR was received then pass buffer to inline code movlw 0x0D ; test for CR cpfseq INDF0 ; if equal then skip goto RxNotCR ; otherwise jump to not CR movpf INDF0, TXREG1 ; echo it back to the term bsf u1Flags, RxRdy ; set flag indicating data ready return ; return to restore context and exit isr RxNotCR ; if here then character was not CR ; ; character was not LF or backspace or CR, test for last buffer addr movlw rxBuffer+rxBufferSize-1 ; load last buffer addr cpfseq intRxPtr ; skip if interrupt pointer is equal movpf INDF0, TXREG1 ; otherwise echo it back to the term cpfslt intRxPtr ; skip if interrupt pointer is less than ; otherwise data was placed in last buffer location and is not a CR decf intRxPtr ; so backup isr pointer return ; return to restore context and exit isr ; ;********************************************************************** StartTx ; Kick start UART1 transmitter interrupt service routine ;********************************************************************** ; ; Initialize flags and pointers for interrupt based UART1 transmit ; and load first byte of buffer into TXREG1 to start transmit. ; This function is called by inline code to setup and start UART1 Tx. ; Exit is accomplished by a return. ; ; ***** Variables for UART1 Tx ***** ; cblock ; declare bank 0 variables txPtr ; pointer into Tx buffer used by inline code intTxPtr ; pointer into Tx buffer used by isr endc ; ; ***** Executable code for UART1 Tx kick start ***** ; movwf txPtr ; load output buffer addr into txPtr ; select sfr bank containing UART1 registers movlb 0 ; select sfr bank 0 ; wait for any ongoing buffered Tx activity to complete btfsc u1Flags, TxRdy ; skip when Tx buffer empty goto $-1 ; until then wait ; reset isr uart Tx buffer pointer to equal inline code pointer movfp txPtr, WREG ; fetch inline buffer ptr movwf intTxPtr ; reset isr Tx pointer movwf FSR0 ; load FSR0 tstfsz INDF0 ; test for null char goto $+2 ; if not null keep going return ; otherwise return w/o starting Tx bsf u1Flags, TxRdy ; set flag indicating buffer is ready movpf INDF0, TXREG1 ; put first byte into Tx reg movlb 1 ; select sfr bank 1 for PIE register bsf PIE1, TX1IE ; enable Tx int return ; Tx started, return ; ;********************************************************************** UART1Tx ; UART1 transmitter interrupt service routine ;********************************************************************** ; ; Transmit characters from buffer until 0 or \ is detected. If 0 is ; detected then the end of the buffer has been reached, the TxRdy ; flag is cleared informing inline code that the buffer is available. ; If the \ character is detected then an escape sequence is indicated ; and the next char is interpreted and the control char sent. If the ; next char is not a known escape character then the \ and the char ; are output as text. ; ; This function ; must be terminated by a return to the peripheral isr which restores ; context and performs the retfie. ; ; The following macro causes this function to be called by the ; peripheral interrupt routine when the TX1IF flag is set. This macro ; must be placed immediately following the label at the beginning of ; the isr function and prior to any executable code. ; ; include bit testing at the peripheral int vector at assembly time InstallISR 1, PIR1, TX1IF ; install isr for uart1 tx ; ; ***** Executable code for UART1 Tx isr ***** ; ; select gpr bank containing Rx buffer, pointers and flags movlr 0 ; select gpr bank 0 ; select sfr bank containing UART1 registers movlb 0 ; select sfr bank 0 ; ; if buffer has no data ready then exit btfss u1Flags, TxRdy ; skip if buffer holds data return ; return to restore context and exit isr ; TestTx ; point to next buffer entry incf intTxPtr ; inc isr Tx pointer movfp intTxPtr, FSR0 ; load FSR0 ; ; process special characters ; ; test for 0 indicating end of tx buffer data tstfsz INDF0 ; is next char 0? goto TxNot0 ; if not keep checking bcf u1Flags, TxRdy ; otherwise clear Tx data ready flag movlb 1 ; select sfr bank 1 for PIE register bcf PIE1, TX1IE ; disable Tx int return ; return to restore context and exit isr TxNot0 ; if here then buffer character is not 0 ; ; test for escape sequence character movlw '\\' ; load escape sequence character cpfseq INDF0 ; is next char \? goto WriteTx ; if not write it incf intTxPtr ; otherwise inc isr Tx pointer movfp intTxPtr, FSR0 ; load FSR0 ; determine which special character is requested cpfseq INDF0 ; is next char also \? goto $+3 ; if not keep checking movwf TXREG1 ; otherwise output it return ; return to restore context and exit isr movlw 'a' ; load bell escape character cpfseq INDF0 ; is next char a? goto $+4 ; if not keep checking movlw 0x07 ; otherwise load bell character movwf TXREG1 ; and output it return ; return to restore context and exit isr movlw 'b' ; load backspace escape character cpfseq INDF0 ; is next char b? goto $+4 ; if not keep checking movlw 0x08 ; otherwise load backspace character movwf TXREG1 ; and output it return ; return to restore context and exit isr movlw 'f' ; load form feed escape character cpfseq INDF0 ; is next char f? goto $+4 ; if not keep checking movlw 0x0C ; otherwise load form feed character movwf TXREG1 ; and output it return ; return to restore context and exit isr movlw 'n' ; load new line escape character cpfseq INDF0 ; is next char n? goto $+4 ; if not keep checking movlw 0x0A ; otherwise load new line character movwf TXREG1 ; and output it return ; return to restore context and exit isr movlw 'r' ; load carriage return escape character cpfseq INDF0 ; is next char r? goto $+4 ; if not keep checking movlw 0x0D ; otherwise load carriage return character movwf TXREG1 ; and output it return ; return to restore context and exit isr movlw 't' ; load tab escape character cpfseq INDF0 ; is next char t? goto $+4 ; if not keep checking movlw 0x09 ; otherwise load tab character movwf TXREG1 ; and output it return ; return to restore context and exit isr movlw 'v' ; load vertical tab escape character cpfseq INDF0 ; is next char v? goto $+4 ; if not keep checking movlw 0x0B ; otherwise load vertical tab character movwf TXREG1 ; and output it return ; return to restore context and exit isr ; otherwise output \ char and exit movlw '\\' ; load \ movwf TXREG1 ; and output it decf intTxPtr ; dec isr Tx pointer to prep for next int ; on next Tx int non-escape char after \ will be output return ; return to restore context and exit isr ; WriteTx ; not end of buffer or escape so output next char from buffer movpf INDF0, TXREG1 ; write Tx data into buffer return ; return to restore context and exit isr ;

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