Electrix said:
Jay.slovak said:
Is there a particular reason not to use Timer1 (and do 225 Wake-up cycles)? Or look for some sort of External wake-up source (such as 555 or other PIC), the PIC will sleep forever unless you wake it up. All you need is an interrupt.
Well yes..I wanted the PIC to handle all the operations ..sort of a one man show..I am actually building an environment monitor that takes readings once in an hour, so thats why..
The guys at the Univ of Southampton managed this with a PIC 16F876, they actually had a 4 hour sleep time.
Ref: Environmental Sensor Networks by Kirk Matinez..et al.
Are you sure they put it in sleep?, and if they did it's unlikely they had a four hour sleep time (unless they used an external signal to wake it). As already suggested, it's more likely the used TMR1 to wake it up MUCH more often, and counted the number of wakeups until four hours had passed. You can do the same with the WDT, but the WDT is very inaccurate.
I presume you're looking at sleep mode for power savings?, so I also presume everything else is absolutely zero power (or extremely low)?, or you're wasting your time putting it to sleep - a PIC when running is pretty low consumption anyway!.