AN247 datasheet(24/32 Pages) MICROCHIP

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AN247

DS00247A-page 24

 2003 Microchip Technology Inc.

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

; Function: VOID _PMRead()

;

VOID _PMEraseWrite()

;

; PreCondition:WREG1 and FSR0 must be loaded with the count and address of

;

the source data.

; Input: None.

; Output: None.

; Side Effects: N/A.

; Stack Requirements: N/A

; Overview: These routines are technically not functions since they will not

;

return when called. They have been written in a linear form to

;

save space.Thus 'call' and 'return' instructions are not

;

included, but rather they are implied.

;

These are the program memory read/write functions. Erase is

;

available through control flags. An automatic erase option

;

is also available. A write lock indicator is in place to

;

ensure intentional write operations.

;

Note: write operations must be on 8-byte boundaries and

;

must be 8 bytes long. Also erase operations can only

;

occur on 64-byte boundaries.

;

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

#ifdef ALLOW_GET_CMD

_PMRead:

tblrd*+

; Fill the buffer

movff

TABLAT, POSTINC0

decfsz WREG1, F

bra

_PMRead

; Not finished then repeat

bra

_CANSendResponce

#endif

_PMEraseWrite:

btfss

MODE_AUTO_ERASE

; Erase if auto erase is requested

bra

_PMWrite

_PMErase:

movf

TBLPTRL, W

; Check for a valid 64 byte border

andlw

b'00111111'

bnz

_PMWrite

_PMEraseJp1

movlw

b'10010100'

; Setup erase

rcall

_StartWrite

; Erase the row

_PMWrite:

btfsc

MODE_ERASE_ONLY

; Don't write if erase only is requested

#ifdef ALLOW_GET_CMD

bra

_CANSendAck

#else

bra

_CANMain

#endif

movf

TBLPTRL, W

; Check for a valid 8 byte border

andlw

b'00000111'

bnz

_CANMain

movlw

0x08

movwf

WREG1

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