One possibility to consider. If you do not need all the features of a full-blown RTCC (especially the calendar and alarm), you can implement a real time clock on a PIC18 with just a watch crystal and 2 capacitors - less than $0.30 in cost.



Using the Secondary Oscillator (RC0, RC1, and TIMER1), all it needs is just a few lines of code to implement an interrupt driven real time clock. Look at the data sheet section for TIMER1 for more details.