Software Real-Time Clock on HC12

Hi!

I am trying to implement a software real-time clock on the HC12 using
the timer module. I am pretty much unable to do it at this point and
was hoping that someone could point me in the right direction --
perhaps even coded examples that could serve as a way to better
understand it. I need to keep track of a 24 hour day, no need for any
actual dates. I can code using either assembler or C++. The clock
should run independently so other code can be inserted without effort.

Thanks for all and any help!

Christian

"Christian Winter" <cwinter@gmail.com> wrote in message 
news:1141307328.634244.164220@p10g2000cwp.googlegroups.com...
> Hi!
>
> I am trying to implement a software real-time clock on the HC12 using
> the timer module. I am pretty much unable to do it at this point and
> was hoping that someone could point me in the right direction --
> perhaps even coded examples that could serve as a way to better
> understand it. I need to keep track of a 24 hour day, no need for any
> actual dates. I can code using either assembler or C++. The clock
> should run independently so other code can be inserted without effort.

I suggest you setup a heartbeat interrupt - say 5ms or 1ms, depending on the 
granularity you need - and do the time maintenance therein.

Steve
http://www.fivetrees.com

if (RTC_tick>= XX ){
   	  	seconds++;
		RTC_tick = 0;

  	    if (seconds>=60){
   	  		minutes++;
			seconds = 0;
   	  	}
	  	if (minutes>=60){
   	  		hours++;
			minutes = 0;
   	  	}
	  	if (hours>=24){
   	  		days++;
			hours = 0;
		}
}

You have to define XX based on the heatbeat time you setup.
Eric

With "heartbeat" do you mean using the real-time interrupts? If so, it
would be best if I could set it up such that it is called every second
to increment the clock.

I also found someone suggesting to use the pulse-width modulator, but I
am unsure as to how to do that.

Getting out the HC12 data sheet again...

"Christian Winter" <cwinter@gmail.com> wrote in message 
news:1141351790.680296.112940@e56g2000cwe.googlegroups.com...

> With "heartbeat" do you mean using the real-time interrupts?

I mean use one of the timers to generate a regular interrupt.

> If so, it
> would be best if I could set it up such that it is called every second
> to increment the clock.

If your only realtime requirement is updating the clock, then sure. But one 
often needs to have finer time control than 1s.

> I also found someone suggesting to use the pulse-width modulator, but I
> am unsure as to how to do that.

Errrr.... PWM is not directly appropriate. However the timer may well be a 
potential interrupt source.

> Getting out the HC12 data sheet again...

Good plan ;).

Steve
http://www.fivetrees.com

"Steve at fivetrees" <steve@NOSPAMTAfivetrees.com> writes:
> "Christian Winter" <cwinter@gmail.com> wrote
> 
> > With "heartbeat" do you mean using the real-time interrupts?
> 
> I mean use one of the timers to generate a regular interrupt.
> 
> > If so, it
> > would be best if I could set it up such that it is called every second
> > to increment the clock.
> 
> If your only realtime requirement is updating the clock, then sure. But one 
> often needs to have finer time control than 1s.
> 
> > I also found someone suggesting to use the pulse-width modulator, but I
> > am unsure as to how to do that.
> 
> Errrr.... PWM is not directly appropriate. However the timer may well be a 
> potential interrupt source.
> 
> > Getting out the HC12 data sheet again...
> 
> Good plan ;).

Looking at the data manual finds the Clock Generation Module,
Realtime Interrupt.  Interrupts occur at one of eight
program-selectable rates in binary fractions of oscillator
frequency.  Use a power-of-two oscillator and you can get
exact time-of-day;  otherwise, throw in a fudge factor
from time to time.