Inter-Integrated Circuit (I2C) Interface - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 562

IBCR | 5 RSTA; /* generate a restart condition */

IBDR 5 0xD1; /* send ID and set R/W flag to read */

while(!(IBSR & IBIF));

IBSR 5 IBIF;

if (IBSR & RXAK)

return 2 1; /* if DS1307 did not respond, return error code */

IBCR & 5 , (TXRX 1 TXAK); /* prepare to receive and acknowledge */

temp 5 IBDR; /* a dummy read to trigger nine clock pulses */

for (i 5 0; i , 5; i 11 ) {

while(!(IBSR & IBIF)); /* wait for a byte to shift in */

IBSR 5 IBIF; /* clear the IBIF flag */

cur_time[i] 5 IBDR; /* save the current time in buffer */

} /* also initiate the next read */

while (!(IBSR & IBIF)); /* wait for the receipt of cur_time[5] */

IBSR 5 IBIF; /* clear IBIF flag */

IBCR | 5 TXAK; /* not to acknowledge cur_time[6] */

cur_time[5] 5 IBDR; /* save cur_time[5] and initiate next read */

while (!(IBSR & IBIF));

IBSR 5 IBIF;

IBCR & 5 , MSSL; /* generate stop condition */

cur_time[6] 5 IBDR;

return 0;

}

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Example 11.7
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Write a function to format the time information stored in the array cur_time [0, . . . , 6] so
that it can be displayed on the LCD.
Solution: The time and calendar information are converted and stored in two character arrays:
hms [0, . . . , 11] and mdy [0, . . . , 11]. The array hms [0, . . . , 11] holds the hours, minutes, and seconds,
whereas the array dmy [0, . . . , 11] holds month, date, and year. The format of display is as follows:
In 24-hour mode,
hh:mm:ss:xx
mm:dd:yy
where xx stands for day of week (can be “SU,” “MO,” “TU,” “WE,” “TH,” “FR,” and “SA”).
In 12-hour mode,
hh:mm:ss:ZM
xx:mm:dd:yy
where Z can be 'A' or 'P' to indicate AM or PM and xx stands for day of week.
The following C function will format the current time of day into two strings:
void formatTime(void)
{

char temp3;

temp3 5 cur_time[3] & 0x07; /* extract day-of-week */