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title "Self Programming"
list b=8, r=dec
;########################################################################
; Self programming, based on Microchip AN851
;########################################################################
; This code has been optimized for size so it would fit in 0x100 code words.
; To achieve this, some special tricks had to be used. As a result the code
; may be a little hard to read
;
; The functionality differs from that described in AN851 in the following
; respects:
; 1. No auto baud detection. Communication must take place at 9600 baud.
; 2. Dropped the first <STX> that was used for auto baud detection.
; 3. Dropped the third address byte as it would always be 0.
; 4. The code does not check the last byte of EEPROM data memory to enter boot
; mode. Instead it transmits a <ETX> character and waits up to 1 second for
; a <STX> character.
; 5. The code is designed to be placed in the highest part of memory. That way
; it doesn't interfere with the interrupt code address. It does rely on the
; main program to call the self-program code at an appropriate time.
; 6. Due to the location of the boot loader code, it cannot be protected using
; the code protection bits in the configuration word. This means that the
; boot loader code can also be updated, if necessary.
; 7. The Erase Flash command has been implemented for the PIC16F device.
; 8. The device reset command is 0x08, not any command with a 0 length.
; 9. The version command can be called with a data length of 1-3 words. It will
; report the following information:
; 1. Version
; 2. Boot loader start address
; 3. Boot loader end address
; The software used to reflash the device can use the last two pieces of
; information to determine which part of memory should not be touched.
#include "p16f88.inc"
errorlevel -302, -306
#define MAJOR_VERSION 1
#define MINOR_VERSION 1
#define STX 0x0F
#define ETX 0x04
#define DLE 0x05
CHKSUM equ 0x70
COUNTER equ 0x71
RXDATA equ 0x72
TXDATA equ 0x73
TEMP equ 0x74
DATA_BUFF equ 0x10 ;Start of receive buffer
COMMAND equ 0x10 ;Data mapped in receive buffer
DATA_COUNT equ 0x11
ADDRESS_L equ 0x12
ADDRESS_H equ 0x13
PACKET_DATA equ 0x14
#define SELFRESET PORTB,1
#define RX PORTB,2
#define TX PORTB,5
#ifdef SELFPROGNEW
#define SELFPROG SelfProgNew
#define STARTADDRESS 0x0700
#else
#define SELFPROG SelfProg
#define STARTADDRESS 0x0f00
#endif
global SELFPROG
SELFPROG code STARTADDRESS
;Do not go into selfprog mode after a watchdog timeout reset
SELFPROG btfss STATUS,NOT_TO
return ;Let the main code handle a timeout
bcf INTCON,GIE ;Ignore interrupts
banksel OSCCON
movlw b'01100000' ;Internal oscillator set to 4MHz
movwf OSCCON ;Configure the oscillator
;Set the LEDS as outputs
#ifndef LVP
movlw b'00100111'
#else
movlw b'00101111'
#endif
movwf TRISB
;Configure the comparators and voltage reference
;Allow communication between thermostat and boiler to continue
;while reprogramming the device
movlw b'11100111' ;Pins 3 and 4 are digital ouputs
movwf TRISA
movlw b'00000111' ;A0 through A2 are used for analog I/O
movwf ANSEL
movlw b'11100110' ;Voltage reference at 1.25V
movwf CVRCON
movlw b'00000110' ;Two common reference comps with output
movwf CMCON
;Configure Timer 0 & Watchdog Timer
;Bit 7 RBPU = 1 - Port B pull up disabled
;Bit 6 INTEDG = 1 - Interrupt on rising edge
;Bit 5 T0CS = 0 - Internal clock
;Bit 4 T0SE = 1 - High to low transition
;Bit 3 PSA = 0 - Prescaler assigned to Timer 0
;Bit 2-0 PS = 7 - 1:256 Prescaler
movlw b'11010111'
movwf OPTION_REG
movlw 25 ;9600 baud
movwf SPBRG
movlw b'00100110'
movwf TXSTA ;High speed, Asynchronous, Enabled
bcf STATUS,RP0
bsf RCSTA,SPEN ;Enable serial port
bsf RCSTA,CREN ;Enable receive
;Clear the LEDS
movlw b'11111111'
movwf PORTB
clrf TMR0
movlw 1
call Pause
;Notify the external programming software (Pause returns <ETX>)
call WrRS232
;Programmer should react within 1 second
movlw 16
call Pause
btfss PIR1,RCIF
;No data received, resume the normal program
return
;Check that the received character is <STX>
call RdRS232
skpz
;Other serial data received, resume normal program
return
bsf STATUS,IRP
ReSync movlw DATA_BUFF
movwf FSR
clrf CHKSUM
GetNextDat call RdRS232 ;Get the data
skpnz
goto ReSync ;Found unprotected STX
xorlw STX ^ ETX ;Check for ETX
skpnz
goto CheckSum ;Yes, examine checksum
xorlw ETX ^ DLE ;Check for DLE
skpnz
call RdRS232 ;Yes, get the next byte
movfw RXDATA
movwf INDF ;Store the data
addwf CHKSUM,F ;Get sum
incf FSR,F
goto GetNextDat
CheckSum tstf CHKSUM
skpz
goto StartOfLine
bsf STATUS,RP1
movfw ADDRESS_L
movwf EEADR
movfw ADDRESS_H
movwf EEADRH
movlw PACKET_DATA
movwf FSR
movfw DATA_COUNT
movwf COUNTER
CheckCommand
#ifdef SELFPROGNEW
movlw high ($ + 0x800)
#else
movlw high $
#endif
movwf PCLATH
movfw COMMAND
sublw 8
sublw 8
skpc
goto StartOfLine
addwf PCL,F
goto ReadVersion ;0 Read Version Information
goto ReadProgMem ;1 Read Program Memory
goto WriteProgMem ;2 Write Program Memory
goto EraseProgMem ;3 Erase Program Memory
goto ReadEE ;4 Read EEDATA Memory
goto WriteEE ;5 Write EEDATA Memory
goto StartOfLine ;6 Read Config Memory
goto StartOfLine ;7 Write Config Memory
goto VReset ;8 Reset
VersionData data (MAJOR_VERSION << 8) | MINOR_VERSION
#ifdef SELFPROGNEW
data SELFPROG + 0x800, SelfProgEnd + 0x800
#else
data SELFPROG, SelfProgEnd
#endif
ReadVersion movlw low VersionData
movwf EEADR
#ifdef SELFPROGNEW
movlw high (VersionData + 0x800)
#else
movlw high VersionData
#endif
movwf EEADRH
movlw DATA_BUFF + 2
movwf FSR
ReadProgMem bsf STATUS,RP0
bsf EECON1,EEPGD
bsf EECON1,RD
nop
nop
bcf STATUS,RP0
movfw EEDATA
movwf INDF
incf FSR,F
movfw EEDATH
movwf INDF
incf FSR,F
incf EEADR,F
skpnz
incf EEADRH,F
decfsz COUNTER,F
goto ReadProgMem
WritePacket movlw DATA_BUFF
subwf FSR,W
WritePacketJ1 movwf COUNTER
movlw STX
call WrRS232
clrf CHKSUM
movlw DATA_BUFF
movwf FSR
SendNext movfw INDF
addwf CHKSUM,F
incf FSR,F
call WrData
decfsz COUNTER,F
goto SendNext
comf CHKSUM,W
addlw 1
call WrData ;WrData returns <ETX>
call WrRS232
StartOfLine bcf STATUS,RP1
call RdRS232 ;Look for a start of line
skpnz
goto ReSync
goto StartOfLine
WriteProgMem movlw b'10000100'
call LoadEECon1
movlw b'11111100'
andwf EEADR,F
movlw 4
movwf TEMP
Lp1 movfw INDF
movwf EEDATA
incf FSR,F
movfw INDF
movwf EEDATH
incf FSR,F
call StartWrite
decfsz TEMP,F
goto Lp1
decfsz COUNTER,F
goto WriteProgMem
goto WritePacketJ1
EraseProgMem movlw b'10010100'
call LoadEECon1
movlw 0x1F
iorwf EEADR,F
call StartWrite
decfsz COUNTER,F
goto EraseProgMem
goto WritePacketJ1
ReadEE bsf STATUS,RP0
clrf EECON1
bsf EECON1,RD
bcf STATUS,RP0
movfw EEDATA
movwf INDF
incf FSR,F
incf EEADR,F
decfsz COUNTER,F
goto ReadEE
goto WritePacket
WriteEE movlw b'00000100'
call LoadEECon1
movfw INDF
movwf EEDATA
incf FSR,F
call StartWrite
decfsz COUNTER,F
goto WriteEE
goto WritePacketJ1
WrData movwf TXDATA
xorlw STX
skpnz
goto WrDLE
xorlw STX ^ ETX
skpnz
goto WrDLE
xorlw ETX ^ DLE
skpz
goto WrNext
WrDLE movlw DLE
call WrRS232
WrNext movfw TXDATA
WrRS232 clrwdt
bcf STATUS,RP1
WaitTxEmpty btfss PIR1,TXIF
goto WaitTxEmpty
movwf TXREG
retlw ETX
RdRS232 btfsc RCSTA,OERR
goto VReset
RdLp1 clrwdt
btfss PIR1,RCIF
goto RdLp1
movfw RCREG
movwf RXDATA
xorlw STX
return
LoadEECon1 bsf STATUS,RP0
movwf EECON1
bcf STATUS,RP0
return
StartWrite clrwdt
bsf STATUS,RP0
movlw 0x55
movwf EECON2
movlw 0xAA
movwf EECON2
bsf EECON1,WR
WaitEEWrite btfsc EECON1,WR ;Skipped when writing program memory
goto WaitEEWrite ;Skipped when writing program memory
bcf STATUS,RP0
incf EEADR,F
skpnz
incf EEADRH,F
retlw 1 ;Return length of acknowledgement
Pause clrwdt
btfsc PIR1,RCIF
return
btfss INTCON,TMR0IF
goto Pause
bcf INTCON,TMR0IF
addlw -1
skpz
goto Pause
retlw ETX
;Reset the device via an external connection from an I/O pin to the reset pin.
VReset bcf STATUS,RP1
bcf SELFRESET ;Prepare the output latch
bsf STATUS,RP0
bcf SELFRESET ;Switch the pin to output
;If resetting via the output pin doesn't work, restore all used registers to
;their power-on defaults and jump to address 0.
;Do not simply return because the code that called this routine may have been
;wiped and reprogrammed to something completely different.
movlw b'11111111'
movwf TRISA
movwf TRISB
movwf OPTION_REG
movwf ANSEL
movlw b'00000111'
movwf CMCON
clrf TXSTA
clrf SPBRG
clrf STATUS
clrf RCSTA
clrf INTCON
clrf PCLATH
clrwdt
SelfProgEnd goto 0
end
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