;============================================================================= ; Software License Agreement ; ; The software supplied herewith by Microchip Technology Incorporated ; (the "Company") for its PICmicro® Microcontroller is intended and ; supplied to you, the Company’s customer, for use solely and ; exclusively on Microchip PICmicro Microcontroller products. The ; software is owned by the Company and/or its supplier, and is ; protected under applicable copyright laws. All rights are reserved. ; Any use in violation of the foregoing restrictions may subject the ; user to criminal sanctions under applicable laws, as well as to ; civil liability for the breach of the terms and conditions of this ; license. ; ; THIS SOFTWARE IS PROVIDED IN AN "AS IS" CONDITION. NO WARRANTIES, ; WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT NOT LIMITED ; TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A ; PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. THE COMPANY SHALL NOT, ; IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL OR ; CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER. ; ;============================================================================= ; Filename: boot877.asm ;============================================================================= ; Author: Mike Garbutt ; Company: Microchip Technology Inc. ; Revision: 1.00 ; Date: 26 June 2000 ; Assembled using MPASM V2.40 ;============================================================================= ; Include Files: p16f877.inc V1.00 ;============================================================================= ; Boot code to receive a hex file containing user code from a ; serial port and write it to program memory. Tests a pin to see ; if code should be downloaded. Receives hex file using USART and ; hardware handshaking. Does error checking on data and writes to ; program memory. Waits for reset and then starts user code running. ;============================================================================= list p=16f877, st=OFF, x=OFF, n=0 errorlevel -302 #include __CONFIG _BODEN_OFF & _CP_OFF & _PWRTE_ON & _WDT_OFF & _WRT_ENABLE_ON & _XT_OSC & _DEBUG_OFF & _CPD_OFF & _LVP_OFF ;----------------------------------------------------------------------------- ;Constants TEST_INPUT EQU 0 ;Port B Pin 0 input indicates download RTS_OUTPUT EQU 1 ;Port B Pin 1 output for flow control CTS_INPUT EQU 2 ;Port B Pin 2 input for flow control BAUD_CONSTANT EQU 0x19 ;Constant for baud generator for 9600 baud ;BAUD_CONSTANT EQU 0x0c ;Constant for baud generator for 19200 baud ;Fosc is 4MHz ;----------------------------------------------------------------------------- ;Variables in bank0 CBLOCK 0x20 AddressH: 1 ;flash program memory address high byte AddressL: 1 ;flash program memory address low byte NumWords: 1 ;number of words in line of hex file Checksum: 1 ;byte to hold checksum of incoming data Counter: 1 ;to count words being saved or programmed TestByte: 1 ;byte to show reset vector code received HexByte: 1 ;byte from 2 incoming ascii characters DataPointer: 1 ;pointer to data in buffer DataArray: 0x40 ;buffer for storing incoming data ENDC ;----------------------------------------------------------------------------- ;Macros to select the register bank ;Many bank changes can be optimised when only one STATUS bit changes Bank0 MACRO ;macro to select data RAM bank 0 bcf STATUS,RP0 bcf STATUS,RP1 ENDM Bank1 MACRO ;macro to select data RAM bank 1 bsf STATUS,RP0 bcf STATUS,RP1 ENDM Bank2 MACRO ;macro to select data RAM bank 2 bcf STATUS,RP0 bsf STATUS,RP1 ENDM Bank3 MACRO ;macro to select data RAM bank 3 bsf STATUS,RP0 bsf STATUS,RP1 ENDM ;============================================================================= ;Reset vector code ORG 0x0000 ResetVector: movlw high Main movwf PCLATH ;set page bits for page3 goto Main ;go to boot loader ;============================================================================= ;Start of boot code in upper memory traps accidental entry into boot code area ORG 0x1f20 ;Use last part of page3 for PIC16F876/7 ; ORG 0x0f20 ;Use last part of page1 for PIC16F873/4 ; ORG 0x0720 ;Use last part of page0 for PIC16F870/1 StartOfBoot: movlw high TrapError ;trap if execution runs into boot code movwf PCLATH ;set correct page TrapError: goto TrapError ;trap error and wait for reset ;----------------------------------------------------------------------------- ;Relocated user reset code to jump to start of user code ;Must be in bank0 before jumping to this routine StartUserCode: clrf PCLATH ;set correct page for reset condition nop ;relocated user code replaces this nop nop ;relocated user code replaces this nop nop ;relocated user code replaces this nop nop ;relocated user code replaces this nop movlw high TrapError1 ;trap if no goto in user reset code movwf PCLATH ;set correct page TrapError1: goto TrapError1 ;trap error and wait for reset ;----------------------------------------------------------------------------- ;Program memory location to show whether valid code has been programmed CodeStatus: DA 0x3fff ;0 for valid code, 0x3fff for no code ;----------------------------------------------------------------------------- ;Main boot code routine ;Tests to see if a load should occur and if valid user code exists Main: Bank0 ;change to bank0 in case of soft reset btfss PORTB,TEST_INPUT ;check pin for boot load goto Loader ;if low then do bootload call LoadStatusAddr ;load address of CodeStatus word call FlashRead ;read data at CodeStatus location Bank2 ;change from bank3 to bank2 movf EEDATA,F ;set Z flag if data is zero Bank0 ;change from bank2 to bank0 btfss STATUS,Z ;test Z flag TrapError2: goto TrapError2 ;if not zero then is no valid code goto StartUserCode ;if zero then run user code ;----------------------------------------------------------------------------- ;Start of routine to load and program new code Loader: clrf TestByte ;indicate no reset vector code yet call LoadStatusAddr ;load address of CodeStatus word movlw 0x3f ;load data to indicate no program movwf EEDATH movlw 0xff ;load data to indicate no program movwf EEDATA call FlashWrite ;write new CodeStatus word call SerialSetup ;set up serial port ;----------------------------------------------------------------------------- ;Get new line of hex file starting with ':' ;Get first 8 bytes after ':' and extract address and number of bytes GetNewLine: call SerialReceive ;get new byte from serial port xorlw ':' ;check if ':' received btfss STATUS,Z goto GetNewLine ;if not then wait for next byte clrf Checksum ;start with checksum zero call GetHexByte ;get number of program data bytes in line andlw 0x1F ;limit number in case of error in file movwf NumWords bcf STATUS,C rrf NumWords,F ;divide by 2 to get number of words call GetHexByte ;get upper half of program start address movwf AddressH call GetHexByte ;get lower half of program start address movwf AddressL bcf STATUS,C rrf AddressH,F ;divide address by 2 to get word address rrf AddressL,F call GetHexByte ;get record type xorlw 0x01 btfsc STATUS,Z ;check if end of file record (0x01) goto FileDone ;if end of file then all done movf HexByte,W xorlw 0x00 btfss STATUS,Z ;check if regular line record (0x00) goto LineDone ;if not then ignore line and send '.' movlw 0xe0 addwf AddressH,W ;check if address < 0x2000 btfsc STATUS,C ;which is ID locations and config bits goto LineDone ;if so then ignore line and send '.' ;----------------------------------------------------------------------------- ;Get data bytes and checksum from line of hex file movlw DataArray movwf FSR ;set pointer to start of array movf NumWords,W movwf Counter ;set counter to number of words GetData: call GetHexByte ;get low data byte movwf INDF ;save in array incf FSR,F ;point to high byte call GetHexByte ;get high data byte movwf INDF ;save in array incf FSR,F ;point to next low byte decfsz Counter,F goto GetData call GetHexByte ;get checksum movf Checksum,W ;check if checksum correct btfss STATUS,Z goto ErrorMessage bsf PORTB,RTS_OUTPUT ;set RTS off to stop data being received ;----------------------------------------------------------------------------- ;Get saved data one word at a time to program into flash movlw DataArray movwf FSR ;point to start of array movf NumWords,W movwf Counter ;set counter to half number of bytes ;----------------------------------------------------------------------------- ;Check if address is in reset code area CheckAddress: movf AddressH,W ;checking for boot location code btfss STATUS,Z ;test if AddressH is zero goto CheckAddress1 ;if not go check if reset code received movlw 0xfc addwf AddressL,W ;add 0xfc (-4) to address btfsc STATUS,C ;no carry means address < 4 goto CheckAddress1 ;if not go check if reset code received bsf TestByte,0 ;show that reset vector code received movf AddressL,W ;relocate addresses 0-3 to new location addlw low (StartUserCode + 1) ;add low address to new location Bank2 ;change from bank0 to bank2 movwf EEADR ;load new low address movlw high (StartUserCode + 1) ;get new location high address movwf EEADRH ;load high address goto LoadData ;go get data byte and program into flash ;----------------------------------------------------------------------------- ;Check if reset code has been received ;Check if address is too high and conflicts with boot loader CheckAddress1: btfss TestByte,0 ;check if reset vector code received first goto ErrorMessage ;if not then error movlw high StartOfBoot ;get high byte of address subwf AddressH,W btfss STATUS,C ;test if less than boot code address goto LoadAddress ;yes so continue with write btfss STATUS,Z ;test if equal to boot code address goto ErrorMessage ;no so error in high byte of address movlw low StartOfBoot ;get low byte of address subwf AddressL,W btfsc STATUS,C ;test if less than boot code address goto ErrorMessage ;no so error in address ;----------------------------------------------------------------------------- ;Load address and data and write data into flash LoadAddress: movf AddressH,W ;get high address Bank2 ;change from bank0 to bank2 movwf EEADRH ;load high address Bank0 ;change from bank2 to bank0 movf AddressL,W ;get low address Bank2 ;change from bank0 to bank2 movwf EEADR ;load low address LoadData: movf INDF,W ;get low byte from array movwf EEDATA ;load low byte incf FSR,F ;point to high data byte movf INDF,W ;get high byte from array movwf EEDATH ;load high byte incf FSR,F ;point to next low data byte call FlashWrite ;write data to program memory Bank0 ;change from bank3 to bank0 incfsz AddressL,F ;increment low address byte goto CheckLineDone ;check for rollover incf AddressH,F ;if so then increment high address byte CheckLineDone: decfsz Counter,F ;check if all words have been programmed goto CheckAddress ;if not then go program next word ;----------------------------------------------------------------------------- ;Done programming line of file LineDone: movlw '.' ;line has been programmed so call SerialTransmit ;transmit progress indicator back goto GetNewLine ;go get next line hex file ;----------------------------------------------------------------------------- ;Done programming file so send success indicator and trap execution until reset FileDone: movlw 'S' ;programming complete so call SerialTransmit ;transmit success indicator back call LoadStatusAddr ;load address of CodeStatus word clrf EEDATH ;load data to indicate program exists clrf EEDATA ;load data to indicate program exists call FlashWrite TrapFileDone: goto TrapFileDone ;all done so wait for reset ;----------------------------------------------------------------------------- ;Error in hex file so send failure indicator and trap error ErrorMessage: movlw 'F' ;error occurred so call SerialTransmit ;transmit failure indicator back TrapError3: goto TrapError3 ;trap error and wait for reset ;----------------------------------------------------------------------------- ;Load address of CodeStatus word into flash memory address registers ;This routine returns in bank2 LoadStatusAddr: Bank2 ;change from bank0 to bank2 movlw high CodeStatus ;load high addr of CodeStatus location movwf EEADRH movlw low CodeStatus ;load low addr of CodeStatus location movwf EEADR return ;----------------------------------------------------------------------------- ;Receive two ascii digits and convert into one hex byte ;This routine returns in bank0 GetHexByte: call SerialReceive ;get new byte from serial port addlw 0xbf ;add -'A' to Ascii high byte btfss STATUS,C ;check if positive addlw 0x07 ;if not, add 17 ('0' to '9') addlw 0x0a ;else add 10 ('A' to 'F') movwf HexByte ;save nibble swapf HexByte,F ;move nibble to high position call SerialReceive ;get new byte from serial port addlw 0xbf ;add -'A' to Ascii low byte btfss STATUS,C ;check if positive addlw 0x07 ;if not, add 17 ('0' to '9') addlw 0x0a ;else add 10 ('A' to 'F') iorwf HexByte,F ;add low nibble to high nibble movf HexByte,W ;put result in W reg addwf Checksum,F ;add to cumulative checksum return ;----------------------------------------------------------------------------- ;Set up USART for asynchronous comms ;Routine is only called once and can be placed in-line saving a call and return ;This routine returns in bank0 SerialSetup: Bank0 ;change from bank3 to bank0 bsf PORTB,RTS_OUTPUT ;set RTS off before setting as output Bank1 ;change from bank0 to bank1 bcf TRISB,RTS_OUTPUT ;enable RTS pin as output movlw BAUD_CONSTANT ;set baud rate 9600 for 4Mhz clock movwf SPBRG bsf TXSTA,BRGH ;baud rate high speed option bsf TXSTA,TXEN ;enable transmission Bank0 ;change from bank1 to bank0 bsf RCSTA,CREN ;enable reception bsf RCSTA,SPEN ;enable serial port return ;----------------------------------------------------------------------------- ;Wait for byte to be received in USART and return with byte in W ;This routine returns in bank0 SerialReceive: Bank0 ;change from unknown bank to bank0 bcf PORTB,RTS_OUTPUT ;set RTS on for data to be received btfss PIR1,RCIF ;check if data received goto $-1 ;wait until new data movf RCREG,W ;get received data into W return ;----------------------------------------------------------------------------- ;Transmit byte in W register from USART ;This routine returns in bank0 SerialTransmit: Bank0 ;change from unknown bank to bank0 btfsc PORTB,CTS_INPUT ;check CTS to see if data can be sent goto $-1 btfss PIR1,TXIF ;check that buffer is empty goto $-1 movwf TXREG ;transmit byte return ;----------------------------------------------------------------------------- ;Write to a location in the flash program memory ;Address in EEADRH and EEADR, data in EEDATH and EEDATA ;This routine returns in bank3 FlashWrite: Bank3 ;change from bank2 to bank3 movlw 0x84 ;enable writes to program flash movwf EECON1 movlw 0x55 ;do timed access writes movwf EECON2 movlw 0xaa movwf EECON2 bsf EECON1,WR ;begin writing to flash nop ;processor halts here while writing nop return ;----------------------------------------------------------------------------- ;Read from a location in the flash program memory ;Address is in EEADRH and EEADR, data returned in EEDATH and EEDATA ;Routine is only called once and can be placed in-line saving a call and return ;This routine returns in bank3 and is called when in bank2 FlashRead: movlw 0x1f ;keep address within range andwf EEADRH,F Bank3 ;change from bank2 to bank3 movlw 0x80 ;enable reads from program flash movwf EECON1 bsf EECON1,RD ;read from flash nop ;processor waits while reading nop return ;----------------------------------------------------------------------------- END