Can I use this crystal with the Propeller

Lord Steve

I have a difficult time understanding some of the requirements of a crystal to be hooked up to the propeller.· I don't get series-mode, parallel-mode, HC/US-29 or whatever.· I usually use oscillators, but I thought I would give crystals a try since they use less power, according to my current understanding.

So, can I use the 12.5 MHz crystal linked-to·below with the Propeller and PLL8x?· (Yes, I want to overclock to 100MHz).

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=300-8432-ND

Thanks!

Mike Green

You're going to have problems for several reasons:

1) The PLL is supposed to work with fundamental crystals from 4 to 8MHz. The Propeller has been used with 10MHz crystals as with the Hydra and the Spin Stamp, but that's considered to be "pushing it". Even though the PLL tap is at 8x, the PLL is still trying to run at 200MHz which is well beyond its range.

2) The crystal load capacitance is specified as 18pF. You would need to use the XTAL3 setting to get something close to that. The other settings are higher and will shift the crystal frequency from its specified frequency.

stevenmess2004

If you want to run at 100MHz you'd be better off using a 6.25MHz crystal.

Lord Steve

I see.· Thank you.

Does there exist a 6.25 MHz crystal that will work with the Propeller and is available for purchase in the US?
·

Mike Green

You can order small quantities (from 1 up) of custom crystals here: www.icmfg.com/buildcrystal.html.

stevenmess2004

Try this link www.alltronics.com/cgi-bin/item/XTAL_6_25MHZ/16/6.25MHZ-CRYSTAL

Lord Steve

Hey, all.· Thanks for your help.· I don't have any 6.25 MHz crystals or oscillators, but I do have an SX28 and a 75 MHz oscillator! [noparse]:D[/noparse]
This SX program was used to run my Propeller at 100 MHz by hooking RA.0 to the XI pin of the Propeller:

 DEVICE SX28AC
 DEVICE OSCHS2
 DEVICE TURBO
 DEVICE OPTIONX
 DEVICE IFBD
 IRC_CAL IRC_SLOW
 ID 'DIVBY12 '
 RESET Start
 FREQ 75_000_000
 ORG $000
Start:
 clrb ra.0
 mode $0F
 mov w, #%1111_1110
 mov !ra, w
 mode $0E
 mov w, #%0000_0001
 mov !ra, w
 mov w, #%0000_0000
 mov !rb, w
 mov !rc, w
:loop
 setb ra.0
 nop
 nop
 nop
 nop
 nop
 clrb ra.0
 nop
 nop
 jmp :loop

hinv

@stevenmess2004. I followed the link, but it doesn't give the specs. Is it in the same package? Is it within the pf range? Have you ordered one from there and gotten it to work?

Thanks,
Doug

stevenmess2004

I haven't used it but the link came from here www.rayslogic.com/propeller/Programming/RaysStuff/RaysStuff.htm which I believe is Raymonds (may not be right) website and he appears to have used it.