;=============================================================================

; Micro Control Journal

; PicBoot1.asm

;

; Revision: 1.00

; Date: October 6, 2000

;=============================================================================

list p=16f876, st=OFF, x=OFF, n=0

errorlevel -302

#include <p16f876.inc>

__CONFIG _BODEN_OFF & _CP_OFF & _PWRTE_ON & _WDT_OFF & _WRT_ENABLE_ON & _XT_OSC & _DEBUG_OFF & _CPD_OFF & _LVP_OFF

;-----------------------------------------------------------------------------

; Constants

; =========

DLY_COUNTT EQU 10

DLY_COUNTH EQU .125

DLY_COUNTL EQU .250

Num_Of_Tries EQU 3 ; Number of tries before exiting to supposed user code

BAUD EQU 0x19 ; 9600 baud at 4.00 MHz

;-----------------------------------------------------------------------------

; Variables bank0

; ===============

CBLOCK 0x20

AdrsH: 1 ; Location of High Byte of flash memory adrs

AdrsL: 1 ; Location of High Byte of flash memory adrs

Count: 1 ; Word Count in this line

HexByte: 1 ; 2 Hex digits

Low_Byte: 1

High_Byte: 1

CountT: 1 ; Top byte of delay variable

CountH: 1 ; High byte of delay variable

CountL: 1 ; Low byte of delay variable

ENDC

;-----------------------------------------------------------------------------

; Macros for register bank selection

; ==================================

Bank0 MACRO ;Bank 0

bcf STATUS,RP0

bcf STATUS,RP1

ENDM

Bank1 MACRO ;Bank 1

bsf STATUS,RP0

bcf STATUS,RP1

ENDM

Bank2 MACRO ;Bank 2

bcf STATUS,RP0

bsf STATUS,RP1

ENDM

Bank3 MACRO ;Bank 3

bsf STATUS,RP0

bsf STATUS,RP1

ENDM

;=============================================================================

; Normal Reset Vector

; ===================

ORG 0x0000

movlw high Boot

movwf PCLATH ;set page bits for page3

goto Boot ;go to boot loader

ORG 0x1EF0 ; For Flash Module - PIC16F876

Start_Of_User_Code:

; Place user code here *****

; ============================================================================

; Start of the Bootloader Code

; ============================================================================

ORG 0x1f00 ; For Flash Module - PIC16F876

Boot:

Bank0

call Init_Serial ; Initialize serial port

movlw Num_Of_Tries

movwf Count

Get_Cmd:

btfss PIR1,RCIF ; Check if Rx flag set

call Delay ; If not kill time

movf RCREG,W ; Char received. Read data into W

decfsz Count ; If num of tries done then assume NO BootLoad

goto Get_Cmd

goto EXIT ; Exit and jump to user code

; Get a line of hex file

Get_Colon:

call Get_Char_e ; Get a char from serial port & echo

xorlw ':' ; Is it ':' ?

btfss STATUS,Z

goto Get_Colon ; If not, repeat till ':' received

; Get the number of data bytes & limit to 10H

; Echo each char as it is received.

call Get_2HexDigits_e

andlw 0x1F

movwf Count

; Data will be received as Byte (2 hex digits)

; Divide the count by 2 to get number of Words

; Echo each char as it is received.

bcf STATUS,C

rrf Count

; Get Program address

; Echo each char as it is received.

call Get_2HexDigits_e

; Upper Byte of address

movwf AdrsH

call Get_2HexDigits_e

; Lower Byte of address

movwf AdrsL

; In PIC program address is indicate in Words and not in Bytes

; Divide the address by 2 to get word address

bcf STATUS,C

rrf AdrsH

rrf AdrsL

Get_Data:

; Get data bytes

; Echo each char as it is received.

call Get_2HexDigits_e ; Receive low data byte

movwf Low_Byte

call Get_2HexDigits_e ; Receive high data byte

movwf High_Byte

Load_Adrs:

; Program flash memory

; Load address into flash program address register

movf AdrsH,W ; Read high address

Bank2

movwf EEADRH ; Load high address

Bank0

movf AdrsL,W ; Read low address

Bank2

movwf EEADR ; Load low address

Load_Data:

; Load data into flash program data register

Bank0

movf Low_Byte,W ; Read low byte

Bank2

movwf EEDATA ; Store low byte

Bank0

movf High_Byte,W ; Read high byte

Bank2

movwf EEDATH ; Store high byte

call Flash_WR ; Program the data in Flash memory

; Increment 16 bit program memory address

Bank0

incfsz AdrsL

goto Next_1

incf AdrsH

Next_1:

decfsz Count ; Check if done

goto Get_Data ; Else get next data word & program

; This line of code is programmed

; Transmit prompt indicating that this line is done

movlw '>'

call Tx_Char

goto Get_Colon ; Get next line

Wait_Here:

goto Wait_Here ; If reached here, then wait for reset

EXIT:

goto Start_Of_User_Code

; Jump to user code, which is assumed to start

; at 0x1EF0

; -----------------------------------------------------------------------------

; *****************************************************************************

; Get_2HexDigits_e

; *****************************************************************************

; Receive two ascii digits and pack these into one hex byte

; Each character is echoed as it is received.

; This routine returns in bank0

; EXIT:

; W contains the Byte

Get_2HexDigits_e:

call Get_Char_e ;get new byte from serial port

addlw 0xbf ; Add -'A'

btfss STATUS,C ; If overflow then number >= 0A (10d)

addlw 0x07 ; It is smaller add 17 ('0' to '9')

addlw 0x0a ; Add 10 and ignore overflow

movwf HexByte ; Store digit (B3-B0)

swapf HexByte ; Shift to MSNibble (B7-B4)

call Get_Char_e ; Read another byte from serial port

addlw 0xbf

btfss STATUS,C

addlw 0x07

addlw 0x0a

iorwf HexByte ; Pack two digits

movf HexByte,W ; Place result in W reg

return

; End of Get_2HexDigits_e

;-----------------------------------------------------------------------------

; *****************************************************************************

; Init_Serial

; *****************************************************************************

; Initialize serial port

;Exit: In bank 0

Init_Serial:

Bank1 ; Bank1

movlw BAUD ; 9600 Baud at 4Mhz Xtal

movwf SPBRG

bsf TXSTA,BRGH ; High speed option

bsf TXSTA,TXEN ; Enable transmitter

Bank0 ; Bank1

bsf RCSTA,CREN ; Enable receiver

bsf RCSTA,SPEN ; Enable serial port

return

; End of Init_Serial

;-----------------------------------------------------------------------------

; *****************************************************************************

; Get_Char

; *****************************************************************************

; Wait for a character

; EXIT:

; W: Char Received

; Bank 0

SerialReceive:

Get_Char:

Bank0 ; Bank 0

Get_Char1:

btfss PIR1,RCIF ; Check if Rx flag set

goto Get_Char1 ;If not check again

movf RCREG,W ;Char received. Read data into W

return

; End of Get_Char

;-----------------------------------------------------------------------------

; *****************************************************************************

; Get_Char_e

; *****************************************************************************

; Wait for a character

; EXIT:

; W: Char Received

; Bank 0

Get_Char_e:

Bank0 ; Bank 0

Get_Char_e1:

btfss PIR1,RCIF ; Check if Rx flag set

goto Get_Char_e1 ;If not check again

movf RCREG,W ;Char received. Read data into W

; The next four lines of code are not needed as the code will automatically

; run into the following Tx_Char routine. These are reproduced here

; for clarity.

Tx_Char_e1:

btfss PIR1,TXIF ; Wait till Tx buffer is empty

goto Tx_Char_e1

movwf TXREG ; Tx char

return

;-----------------------------------------------------------------------------

; *****************************************************************************

; Tx_Char

; *****************************************************************************

; Transmit a character

; ENTRY:

; W: Char to be transmitted

; EXIT:

; Bank 0

SerialTransmit:

Tx_Char:

Bank0 ; Bank 0

Tx_Char1:

btfss PIR1,TXIF ; Wait till Tx buffer is empty

goto Tx_Char1

movwf TXREG ; Tx char

return

; End of Tx_Char

;-----------------------------------------------------------------------------

; *****************************************************************************

; Flash_WR

; *****************************************************************************

; Program the flash program memory

; ENTRY:

; EEADRH and EEADR: Program address

; EEDATH and EEDATA: Data to be programmed

; EXIT:

; Bank3

Flash_WR:

Bank3

bsf EECON1,EEPGD ; Enable flash programming

bsf EECON1,WREN ; Enable write to flash memory

movlw 0x55

movwf EECON2

movlw 0xAA

movwf EECON2

bsf EECON1,WR ; Start program operation

nop

bcf EECON1,WREN ; Disable write to flash

return

; End of Flash_WR

;-----------------------------------------------------------------------------

; *****************************************************************************

; Delay

; *****************************************************************************

; EXIT:

; Bank0

Delay:

movlw DLY_COUNTT

movwf CountT

Delay_1:

movlw DLY_COUNTH

movwf CountH

Delay_2:

movlw DLY_COUNTL

movwf CountL

Delay_3:

decfsz CountL

goto Delay_3

decfsz CountH

goto Delay_2

decfsz CountT

goto Delay_1

nop

return

; End of Delay

;-----------------------------------------------------------------------------

; **********************************************************************

END

; **********************************************************************