Inter-Integrated Circuit (I2C) Interface - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 576

Step 10
Assert the stop condition.
The assembly program that implements this procedure is as follows:
readConf

ldaa #$92 ; generate a start condition and send out DS1631A

jsr sendSlaveID ; ID

brclr IBSR,RXAK,rdConfok1 ; did DS1631A acknowledge?

ldab #$FF ; return error code 2 1

rts

rdConfok1 movb #$AC,IBDR ; send out the Access Conf command

brclr IBSR,IBIF,* ; wait until the command is shifted out

movb #IBIF,IBSR ; clear the IBIF flag

brclr IBSR,RXAK,rdConfok2 ; did DS1631A acknowledge?

ldab #$FF ; return error code 2 1

rts

rdConfok2 bset IBCR,RSTA ; generate a restart condition

movb #$93,IBDR ; send out slave ID and set R/W bit to 1

brclr IBSR,IBIF,* ; wait until the command is shifted out

movb #IBIF,IBSR ; clear the IBIF flag

brclr IBSR,RXAK,rdConfok3 ; did DS1631A acknowledge?

ldab #$FF ; return error code 2 1

rts

rdConfok3 bclr IBCR,TXRX ; prepare to read

bset IBCR,TXAK ; prepare to send NACK

ldaa IBDR ; perform a dummy read to trigger nine clock pulses

brclr IBSR,IBIF,* ; wait until a byte has been shifted in

movb #IBIF,IBSR ; clear the IBIF flag

bclr IBCR,MSSL ; generate a stop condition

ldab IBDR ; place the Conf register value in B

rts
The C language version of the function is as follows:
char readConf(void)
{
char temp;
sendSlaveID(0x92);
if(IBSR & RXAK) /* did DS1631A acknowledge? */

return 2 1;
IBDR 5 0xAC; /* send command to access Conf register */

while(!(IBSR & IBIF));
IBSR 5 IBIF;
if (IBSR & RXAK)
return 2 1;
IBCR | 5 RSTA;

/* generate a restart condition */

IBDR 5 0x93; /* send out ID and set R/W to 1 */

while(!(IBSR & IBIF));
IBSR 5 IBIF;
if (IBSR & RXAK)
return 2 1;
IBCR & 5 , TXRX; /* prepare to receive */