Configure the internal timer3 on X2 parts.

[techElder]

I'm trying to figure out how timer3 works.

Is the accuracy of this quote from Picaxe Manual 2 "BASIC COMMANDS", page 204, common knowledge?

The internal timer counts, when enabled, at a rate of (1/resonator speed) / 4. This means, for instance, at 8MHz the internal timer increment occurs every 0.5us. This value can be optionally scaled by the prescale value (set via bits 5:4) , so with a 1: 8 prescale the increment will occur every 4us (8 x 0.5us).

Confusing at best ...

 

[tjetson]

A quick calculation leads me to believe it should be (1/speed)/0.25

Example:
8 MHz = 8,000,000 Hz

1/8,000,000 = 0.000000125
0.000000125 / 0.25 = 0.0000005 seconds,
or 0.0005 milliseconds, or 0.5 microseconds.


A typo perhaps, or are my calculations wrong?

 

[techElder]

I did finally find where Hippy noted the error back in 2009.

The "/4" should have been "*4" as you noted with your "/0.25".

http://www.picaxeforum.co.uk/showthread.php?t=12919

 

[MartinM57]

It's a documentation issue, alluded to over a year ago and not yet fixed...

http://www.picaxeforum.co.uk/showthread.php?t=12919&highlight=timer3