Quick Prop Question

tom90

Hey All,

Can I use the prop with a 12 MHz oscillator? Will this cause any problems?
Also, what is the fastest that the prop can operate?

Thanks
Tom

Post Edited (tom90) : 1/29/2009 7:49:36 PM GMT

Rayman

You can use a 12 MHz oscillator, but not a 12 MHz crystal...
See the end of the new datasheet for max speeds...

Paul Baker

I strongly recommend you do not use 12 MHz unless this is the exact frequency you want to operate at. The reason being is that you cannot use a PLL with a 12 MHz crystal. The chip and PLL speeds are stated in the data sheet, thier nominal rated speeds are 80 and 128 MHz respectivley. This means that the chip is rated to run up to 80MHz, if you want to push it beyond this check the datasheet, but individual chips are not guaranteed to run beyond 80 MHz. The PLL when used automatically multiplies the crystal frequency by 16, it is guaranteed to run up to 128 MHz but will typically operate up to 160 without issue. If you multiply 12 by 16 you get 192 MHz which is too much for the PLL to handle.

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Paul Baker

hippy

There's been some success with using 14.31818MHz crystals, but as you will be capped at PLL8x, 12MHz would be 96MHz so you're no better off than having used 6MHz + PLL16x.

Just short of 120MHz seems to be the fastest the Propeller will work at under 'normal conditions' ( eg, unmodified protoboard ), 80MHz guaranteed, while 96MHz and 100MHz seem to have given no reported problems ( Parallax test to 104MHz prior to shipping from an earlier posting by Chip ), above that, YMMV.

http://propeller.wikispaces.com/Oscillator