Controller Area Network (CAN) - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 676

Solution: The first step is to enter the initialization mode and make sure the initialization is
entered. This can be done as follows:
bset CAN1CTL0,INITRQ
brclr CAN1CTL1,INITAK,*
The assembly program that performs the desired configuration is as follows:
openCan1 bset CAN1CTL1,CANE ; required after reset

bset CAN1CTL0,INITRQ ; request to enter initialization mode

w1 brclr CAN1CTL1,INITAK,w1 ; make sure initialization mode is entered

movb #$84,CAN1CTL1 ; enable CAN1, select oscillator as clock source

; enable wake-up filter

movb #$C7,CAN1BTR0 ; set jump width to 4 t Q , prescaler set to 8

movb #$B4,CAN1BTR1 ; set phase_seg2 to 4 t Q , phase_seg1 to 4 t Q ,

; set prop_seg to 1 t Q , 3 samples per bit

movb #$54,CAN1IDAR0 ; acceptance identifier T1

movb #$3C,CAN1IDAR1 ; “

movb #$40,CAN1IDAR2 ; “

movb #$00,CAN1IDAR3 ; “

movb #$00,CAN1IDMR0 ; acceptance mask for extended identifier T1

movb #$00,CAN1IDMR1 ; “

movb #$3F,CAN1IDMR2 ; “

movb #$FF,CAN1IDMR3 ; “

movb #$50,CAN1IDAR4 ; acceptance identifier P1

movb #$3C,CAN1IDAR5 ; “

movb #$40,CAN1IDAR6 ; “

movb #$00,CAN1IDAR7 ; “

movb #$00,CAN1IDMR4 ; acceptance mask for extended identifier P1

movb #$00,CAN1IDMR5 ; “

movb #$3F,CAN1IDMR6 ; “

movb #$FF,CAN1IDMR7 ; “

clr CAN1IDAC ; set two 32-bit filter mode

movb #$25,CAN1CTL0 ; stop clock on wait mode, enable wake-up

bclr CAN1CTL0,INITRQ ; leave initialization mode

rts
The C language version of the function is as follows:
void openCan1(void)
{

CAN1CTL1 | 5 CANE; /* enable CAN, required after reset */

CAN1CTL0 | 5 INITRQ; /* request to enter initialization mode */

while(!(CAN1CTL1&INITAK)); /* wait until initialization mode is entered */

CAN1CTL1 5 0x84; /* enable CAN1, select oscillator as MSCAN clock

source, enable wake-up filter */

CAN1BTR0 5 0xC7; /* set SJW to 4, set prescaler to 8 */

CAN1BTR1 5 0xB4; /* set phase_seg2 to 4 t Q , phase_seg1 to 4 t Q ,

prop_seg to 1 t Q */

CAN1IDAR0 5 0x54; /* set acceptance identifier T1 */

CAN1IDAR1 5 0x3C; /* “ */

CAN1IDAR2 5 0x40; /* “ */

CAN1IDAR3 5 0x00; /* “ */

CAN1IDMR0 5 0x00; /* acceptance mask for T1 */