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theteaman
Joined: 04 Aug 2006
Posts: 98
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| 18LF25k22 oscillator too fast |
 Posted: Wed Jan 02, 2013 1:50 am |
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Hi
I am using an 18LF25K22 with the fuses
| Code: |
#use delay(clock=20000000, crystal=20000000)
#fuses NOWDT, WDT128, HSH, NOIESO, BROWNOUT, PUT, NOSTVREN, NODEBUG, NOLVP, NOEBTR, NOCPB, NOEBTRB, NOWRTC, NOWRTB, NOFCMEN, NOPBADEN
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and a 20MHz crystal. I set a pin to alternate between high and low every 5000 milliseconds with delay_ms(5000). But on my scope I can clearly see the signal's period is just over 1 second...
VDD is 4.5V.
I'm curious as to why it just won't go at the right speed? Any help appreciated, thanks. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19496
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| Posted: Wed Jan 02, 2013 2:30 am |
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Add NOPLLEN
The default fuse has the PLL enabled, _unless_ you say otherwise. You can always tell by looking at the bit patterns selected at the end of the .LST file, and checking these against the data sheet. It is designed to confuse, since on most chips the default is for the PLL to be 'off'.
Impressive actually that the chip runs at 80MHz.... ;)
Best Wishes |
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theteaman
Joined: 04 Aug 2006
Posts: 98
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| Posted: Wed Jan 02, 2013 2:41 am |
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You sir, just saved me hours more confusion! Thank you! I never thought that the PLL default could be different for different devices.
Thanks again. |
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