Will the propeller work with a resonator?

CJ

like the 20Mhz one on the OEM BS2, or are crystals the only way to go?

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Who says you have to have knowledge to use it?

I've killed a fly with my bare mind.

LoopyByteloose

You don't need to go that high and in fact you cannot.

I believe the specifications are from 4Mhz to 8 Mhz. The Propeller boosts it to a high rate with a multiplier, a PLL device

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Post Edited (Kramer) : 4/5/2006 4:34:24 AM GMT

pjv

Hi CJ;

I'd like to correct what Kramer stated....

Sure it can..... all the way up to (currently) 80 MHz. In such a case the PLL multiplier is configured to be disabled. With the PLL I was able to get mine up to about 95Mhz.

When the Propeller boots, first it runs on its internal RC oscillator, and then once it loads the Spin interpreter into Cog0, your program sets the oscillator configuration details, and away it goes.

Furthermore, I believe that future incarnations of the silicon will in fact run at higher speeds (native, and pll mode to 128 Mhz) as well as draw less power.

Cheers,

Peter (pjv)

CJ

I was wondering because Jon had mentioned in the "Execution speed" topic,

http://forums.parallax.com/forums/default.aspx?f=25&m=118452

that the pll could be set to 1x, 2x, 4x, 8x, or 16x.
I was primarily wondering if it would be compatible.

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Who says you have to have knowledge to use it?

I've killed a fly with my bare mind.

Jon Williams

The PLL is always there, you simply select a tap (1x is assumed unless you specify otherwise). On our current silicon you should not select a combination that causes the system clock to be above 80 MHz. If you use a 5 MHz crystal, you can use 16x; if you use a 20 MHz crystal, you should use nothing higher than 4x.

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Jon Williams
Applications Engineer, Parallax

CJ

thanks

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Who says you have to have knowledge to use it?

I've killed a fly with my bare mind.

Tracy Allen

Jon,

I might be wrong about this, but I think that when the PLL is enabled, it always operates at 16x, and the taps select frequencies that are divided down from that. The range of xtals for use with the PLL is limited to 4--8mhz, so the 16x PLL can operate between 64 and 128mhz. It would not be possible to use the PLL with a 20mhz xtal. It would be possible to use a 20mhz or 50mhz xtal directly, though, without the PLL enabled.

With the prototype chips, the recommended maximum with the PLL was 80mhz, a 5mhz xtal or resonator.

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Tracy Allen
www.emesystems.com

LoopyByteloose

If there a significant advantage in regards to power consumption to use one or the other?

Alternatively, is there a significant EMI advantage to using one or the other?

I had just presumed that the 4-8Mhz had some advantage other than it is easier to buy crystals and resonators in that range.

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

pjv

Hi Kramer;

Altough I have not yet tested this, I expect that the X16PLL approach off a 5 MHz crystal will be a little quieter, but that is yet to be confirmed.

Probably some time after a lot of other issues are investigated.

Cheers,

Peter (pjv)

LoopyByteloose

Thank you, I got that impression from somewhere.
Maybe I just inferred it from past threads on EMI at high clock rates.

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

parts-man73

All the diagrams I have seen do not show capacitors with the crystal. Is this not nessasary? or should they be used?

Thanks again,
Brian

cgracey

For crystals and resonators, there are three modes of oscillator operation. The loading caps and series resistor are built-in and variable, based on mode. So, you only need to connect the resonator or crystal directly to the XIN and XOUT pins - no extra capacitors or resistors are required. Here are the modes:


·

parts-man73 said...
All the diagrams I have seen do not show capacitors with the crystal. Is this not nessasary? or should they be used?

Thanks again,
Brian

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Chip Gracey
Parallax, Inc.

LoopyByteloose

"The loading caps and series resistor are built-in. . . ."

From my understanding, some Murata resonators ALSO have built-in caps. [noparse][[/noparse]The 3-lead version]
I suppose if they work, okay; but it would be best to keep it simple.

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Post Edited (Kramer) : 4/16/2006 11:40:34 AM GMT