Any issues with 10MHz xtal + PLL8x?

Bill Henning

I built another propeller board, and I'm getting some strange results... could it be due to using a 10MHz xtal and PLL8x? I thought I remembered the Hydra using 10MHz/PLL8x..

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mctrivia

I believe the PLL circuit runs at 16x all the time and taps off to get the slower speed. making a 10MHz crystal to fast for the prop to run.

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Mike Green

The Hydra and the Spin Stamp both use 10MHz crystals and PLL8X. I believe the PLL circuit is good up to 160MHz which is why this scheme works. The rest of the system clock circuitry is only good up to about 100MHz and that depends on operating temperature and supply voltage. There's a graph on the Propeller datasheet with this information.

Bill Henning

Thanks guys. I switched back to a 5MHz xtal for now.

Mike Green said...
The Hydra and the Spin Stamp both use 10MHz crystals and PLL8X. I believe the PLL circuit is good up to 160MHz which is why this scheme works. The rest of the system clock circuitry is only good up to about 100MHz and that depends on operating temperature and supply voltage. There's a graph on the Propeller datasheet with this information.

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MagIO2

Could you give more details about the problems you have?

I run my breadboard with 10MHz and did not have any problems yet - besides not being able to run the turbulence demo or from time to time forget to adjust the constants of ObEx code correctly ;o)

Bill Henning

My SPI code for talking to the Winbond flash chips was misbehaving - it was missing seeing the "write completed" status in response to a status command. Weird. I am continuing to investigate today; my best guess is that I damaged the propeller on that board by briefly (accidentally) running it at 160MHz.

MagIO2 said...
Could you give more details about the problems you have?

I run my breadboard with 10MHz and did not have any problems yet - besides not being able to run the turbulence demo or from time to time forget to adjust the constants of ObEx code correctly ;o)

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Sapieha

Hi Bill Henning.

I run one USB ProtoBoard with 15MHz x 8 and communicate with ViewPort very stable.
And have many times started it with x16 with no problems to damage PropChip.
one problem that become with RUN Propeller with 10MHz and biger is to bad capacitor nearest Propeller chip.

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Nothing is impossible, there are only different degrees of difficulty.
For every stupid question there is at least one intelligent answer.
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If you don't ask you won't know.
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Sapieha

Bill Henning

Hi Sapieha,

Thanks! I was able to reproduce the SPI problem on an older hand-wired prototype which worked fine before, so it is probably a software issue.

Sapieha said...
Hi Bill Henning.

I run one USB ProtoBoard with 15MHz x 8 and communicate with ViewPort very stable.
And have many times started it with x16 with no problems to damage PropChip.
one problem that become with RUN Propeller with 10MHz and biger is to bad capacitor nearest Propeller chip.

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www.mikronauts.com - a new blog about microcontrollers

simonl

@Bill: I too use a 10MHz crystal - and have inadvertently run at 160MHz (for a short while) without problem. I have, however, found that I need the following settings for it to be reliable:

    _clkmode = [b]xtal2[/b] + pll8x                           
    _xinfreq = 10_000_000                                'Note Clock Speed for your setup!!

Note the "xtal2" - I think it's down to the type of crystal used (?)

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Cheers,
Simon

---

www.norfolkhelicopterclub.com

“Before you criticize someone, you should walk a mile in their shoes. That way when you criticize them, you are a mile away from them and you have their shoes.” - Jack Handey.

Bill Henning

Thanks, I will try that next time. Right now I want back to a 5MHz xtal.

simonl said...
@Bill: I too use a 10MHz crystal - and have inadvertently run at 160MHz (for a short while) without problem. I have, however, found that I need the following settings for it to be reliable:

    _clkmode = [b]xtal2[/b] + pll8x                           
    _xinfreq = 10_000_000                                'Note Clock Speed for your setup!!

Note the "xtal2" - I think it's down to the type of crystal used (?)

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www.mikronauts.com - a new blog about microcontrollers

Rayman

I played around a lot with the Oled96Prop...

It also uses a 10MHz crystal.· It works fine with one cog at PLL16.· But, as soon as you try to do more cogs, it hangs.· Works just fine at PLL8 with·multiple cogs.

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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

Timothy D. Swieter

I have designed a product that uses the 10MHz. crystal and that product through testing so far has been working well. I use the setting that Simon pointed out. I have two more projects (one with PCBs ordered and another in the middle of design) that uses the 10MHz crystal as well. I use the 10MHz. crystal because I like the SMD packages I found and in brief research for small SMD crystal packages 10MHz is easier to find than 5MHz.

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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
www.tdswieter.com

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Rayman said...

I played around a lot with the Oled96Prop...

It also uses a 10MHz crystal.· It works fine with one cog at PLL16.· But, as soon as you try to do more cogs, it hangs.· Works just fine at PLL8 with·multiple cogs.

Ray,

This very good to know. Up till now I have not used more than one cog on my uOLED96Prop with the 10MHZ xtal. I have bought 2 more from Dontronics that have the 8 MHZ xtal, so·they sould be OK.

Thanks for the heads up!



Jim