Datasheet

PIC18F2585/2680/4585/4680
DS39625C-page 278 Preliminary © 2007 Microchip Technology Inc.
EXAMPLE 23-1: CHANGING TO CONFIGURATION MODE
EXAMPLE 23-2: WIN AND ICODE BITS USAGE IN INTERRUPT SERVICE ROUTINE TO ACCESS
TX/RX BUFFERS
; Request Configuration mode.
MOVLW B’10000000’ ; Set to Configuration Mode.
MOVWF CANCON
; A request to switch to Configuration mode may not be immediately honored.
; Module will wait for CAN bus to be idle before switching to Configuration Mode.
; Request for other modes such as Loopback, Disable etc. may be honored immediately.
; It is always good practice to wait and verify before continuing.
ConfigWait:
MOVF CANSTAT, W ; Read current mode state.
ANDLW B’10000000’ ; Interested in OPMODE bits only.
TSTFSZ WREG ; Is it Configuration mode yet?
BRA ConfigWait ; No. Continue to wait...
; Module is in Configuration mode now.
; Modify configuration registers as required.
; Switch back to Normal mode to be able to communicate.
; Save application required context.
; Poll interrupt flags and determine source of interrupt
; This was found to be CAN interrupt
; TempCANCON and TempCANSTAT are variables defined in Access Bank low
MOVFF CANCON, TempCANCON ; Save CANCON.WIN bits
; This is required to prevent CANCON
; from corrupting CAN buffer access
; in-progress while this interrupt
; occurred
MOVFF CANSTAT, TempCANSTAT ; Save CANSTAT register
; This is required to make sure that
; we use same CANSTAT value rather
; than one changed by another CAN
; interrupt.
MOVF TempCANSTAT, W ; Retrieve ICODE bits
ANDLW B’00001110’
ADDWF PCL, F ; Perform computed GOTO
; to corresponding interrupt cause
BRA NoInterrupt ; 000 = No interrupt
BRA ErrorInterrupt ; 001 = Error interrupt
BRA TXB2Interrupt ; 010 = TXB2 interrupt
BRA TXB1Interrupt ; 011 = TXB1 interrupt
BRA TXB0Interrupt ; 100 = TXB0 interrupt
BRA RXB1Interrupt ; 101 = RXB1 interrupt
BRA RXB0Interrupt ; 110 = RXB0 interrupt
; 111 = Wake-up on interrupt
WakeupInterrupt
BCF PIR3, WAKIF ; Clear the interrupt flag
;
; User code to handle wake-up procedure
;
;
; Continue checking for other interrupt source or return from here
…
NoInterrupt
… ; PC should never vector here. User may
; place a trap such as infinite loop or pin/port
; indication to catch this error.