pic 16f628 internal oscillator question(s)

[Active8]

The PIC has a 4 to 1 instruction cycle. The clkout is 1/4 the clock.

Your point is?

6/4 is 1.5MHz and 1.5*4=6 for a 4MHz clock. I can probably recite
the spec sheet *and* the mid-range ref -- slight exaggeration
intended, mis-spellings, not.

They claim that the PIC12F675 is calibrated to 1% using OSCCAL.

Ser gut (very good.)

Subject: pic 16f628 internal oscillator question(s)

 

[Active8]

I've found that the OSCCAL set at the factory is off by 5 to 10%, contrary
to expectations. The factory is someplace in indochina, I think, so its
probably a temperature thing

LOL. Different definiition of STP?

Now that's a significant fact. Thanks for the heads up.<snip>

 

[Active8]

There was a large batch of 16F chips, where this behaviour occured if you
ran the supply was at one particular end of the allowable range (5v?). If I
remember correctly, they run perfectly 'on frequency' at a lower supply
rail. Basically the oscillator had a problem. However this was not
'universal'.
I'd suspect you had one of these examples.

Best Wishes

The CIQ (Chip In Question) is anly a couple of... well... no
telling how long since it was born. I did run it at 5V, too.

Bottom line to my posts was that the F628's don't have an OSCAL
word. Not sure about C's. There are mid-range PICs that do, though.

 

[Active8]

On Wed, 28 Jan 2004 00:10:59 GMT, Spehro Pefhany <Spehro Pefhany

It's also Vdd-dependent.

And no doubt subject to human error. Could be a rough commute from
the poppy fields areas to the plant. Is that a plant to plant
variance? Pick (ok, scrape) one plant and pick a PIC plant.

 

[Wouter van Ooijen]

They claim that the PIC12F675 is calibrated to 1% using OSCCAL.

But read the datasheet carefully, IIRC that is typical and at 5V, 20C.


Wouter van Ooijen

-- ------------------------------------
http://www.voti.nl
PICmicro chips, programmers, consulting

 

[Spehro Pefhany]

But read the datasheet carefully, IIRC that is typical and at 5V, 20C.

YDNRC, it's guaranteed, but at Vdd = 3.5V and 25°C ;-)

(Parameter F10, DS41190C)

The +/-2% spec is perhaps more useful:
(2.5V <= VDD <= 5.5V, 0°C <= Ta <= 85°C

And there's a +/-5% spec for wide temperature and Vdd.

Best regards,
Spehro Pefhany

 

[Wouter van Ooijen]

YDNRC, it's guaranteed, but at Vdd = 3.5V and 25°C ;-)

I always wonder what such a spec realy means. No reange or tolerance
is pecified for Vdd or temperature, so taken literally it applies only
to exactly 3.5 and 25, which is impossible to achieve.


Wouter van Ooijen

-- ------------------------------------
http://www.voti.nl
PICmicro chips, programmers, consulting

 

[Spehro Pefhany]

I always wonder what such a spec realy means. No reange or tolerance
is pecified for Vdd or temperature, so taken literally it applies only
to exactly 3.5 and 25, which is impossible to achieve.

It doesn't guarantee much of anything, of course, but from the fixed
point and typical/3-sigma variation curves, with some safety factor,
you might be able to get a good night's sleep. Clearly, it is NOT
guaranteed to be within +/-1% under any practical set of conditions.

Best regards,
Spehro Pefhany