The HCS12 does not have a native clock you can read to get out date and time. You must program a clock yourself. An
excellent reference which contains all the code you need for a real time clock is "Programming the Motorola M68HC12
Family", by Gordon Doughman, 2000, Annabooks, http://www.annabooks.com/. That program uses power line interrupts
for accuracy.
My own HCS12 runs a PLL at 48 Mhz and generates 30 interrupts per second using the Modulus counter. The program
maintains a set of counters for seconds, minutes, hours, days, months, and year. My board's crystal oscillator is
accurate enough for my needs.
