In SX Microcontrollers, SX/B Compiler and SX-Key Tool, dkemppai wrote:

[quote="pjv"]
Hi Bean;

Something you may not be aware of because it's not really dealt with in the SX documentation, and that is anytime you do a write, or read-modify-write, to the RTCC, it "eats" 3 clock cycles. So if your trick writes to the RTCC - and I suspect CLR RTCC might fall into that category but needs to be confirmed- then you need to account for those 3 cycles.

And in testing this, please be careful, as the debug IDE will not show the proper count....... if I recall correctly, it is out by one.

Cheers,

Peter (pjv)[/quote]This my version of modifying the RTCC time...


[code]
mov RTCC,#47 ;Sets RTCC Cycles = ((255 - x) +3 +3 +3) 
;Where x is (mov RTCC,#x) 
;for x = #47, RTCC happens every 217  
[/code]
I've experimentally found that the interrupt taks 3 cycles in, 3 cycles out, and there are 3 more lost in the confusion. I measured the time on an o-scope...   ...and adjust my math accordingly. It also took a while to figure out what was going on. Of course I wasn't using a prescaler on anything here ;) 
 

-Dan

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