AN247 datasheet(21/32 Pages) MICROCHIP

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 2003 Microchip Technology Inc.

DS00247A-page 21

AN247

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

; Function: VOID _ReadWriteMemory()

;

; PreCondition:Enter only after _CANMain().

; Input: None.

; Output: None.

; Side Effects: N/A.

; Stack Requirements: N/A

; Overview: This routine is technically not a function since it will not

;

return when called. It has been written in a linear form to

;

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

;

included, but rather they are implied.

;

This is the memory I/O engine. A total of eight data

;

bytes are received and decoded. In addition two control

;

bits are received, put/get and control/data.

;

A pointer to the buffer is passed via FSR0 for reading or writing.

;

The control register set contains a pointer, some control bits

;

and special command registers.

;

Control

;

;

Data

;

;

PG bit:

Put = 0, Get = 1

;

CD bit:

Control = 0, Data = 1

;

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

_ReadWriteMemory:

btfscCAN_CD_BIT

; Write/read data or control registers

bra

_DataReg

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

; This routine reads or writes the bootloader control registers,

; then executes any immediate command received.

_ControlReg

lfsr

1, _bootCtlMem

_ControlRegLp1

#ifdef ALLOW_GET_CMD

btfsc

CAN_PG_BIT

; or copy control registers to buffer

movff

POSTINC1, POSTINC0

btfss

CAN_PG_BIT

; Copy the buffer to the control registers

#endif

movff

POSTINC0, POSTINC1

decfsz WREG1, F

bra

_ControlRegLp1

#ifdef ALLOW_GET_CMD

btfsc

CAN_PG_BIT

bra

_CANSendResponce; Send response if get

#endif

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

; This is a no operation command.

movf

_bootSpcCmd, W; NOP Command

_SpecialCmdJp2; or send an acknowledge

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

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