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Gabriel
Joined: 03 Aug 2009
Posts: 1067
Location: Panama
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| changing frequencies |
 Posted: Fri Aug 03, 2012 8:21 pm |
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hi,
First time trying this frequency changing deal...
from reading some of the posts here i concluded that:
at the beginning of my main:
| Code: | | while(!((SETUP_OSCILLATOR(OSC_NORMAL))& OSC_STATE_STABLE)); // Waits till oscillator is stable |
Later in Main:
| Code: | | while(!((SETUP_OSCILLATOR(OSC_4MHZ))& OSC_STATE_STABLE)); // Waits till oscillator is stable |
am i actually waiting for it to stabilize? or am i missing something..
seems to be working though...
going from 20M to 4M
16F886.
thanks!
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CCS PCM 5.078 & CCS PCH 5.093 |
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gpsmikey
Joined: 16 Nov 2010
Posts: 588
Location: Kirkland, WA
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| Posted: Fri Aug 03, 2012 9:02 pm |
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I have not done that, but don't forget if you change the osc. freq, you will also change any delay statements and any baud rates you are using.
mikey
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mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3 |
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Gabriel
Joined: 03 Aug 2009
Posts: 1067
Location: Panama
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| Posted: Sat Aug 04, 2012 6:14 am |
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yeap... im _very_ aware of changing the delay statement and baud rates...
im asking this question precisely because im having issues doing just that and i just want to clearout the small things...
i really dont have a clear idea on how to use the OSC_STATE_STABLE value or variable... i dont know what the hell it is ....
the .h file seems (from PCM's Comments on other posts) to mention that its not a return value but a mask to isolate the Setup_oscillator _actual_return value bits.... very confusing.
thanks..
G
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CCS PCM 5.078 & CCS PCH 5.093 |
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dyeatman
Joined: 06 Sep 2003
Posts: 1934
Location: Norman, OK
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| Posted: Sat Aug 04, 2012 7:49 am |
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In section 4.2 (oscillator control) of the datasheet it has this for the 31KHZ and HS oscillators:
| Quote: | bit 2 HTS: HFINTOSC Status bit (High Frequency – 8 MHz to 125 kHz)
1 = HFINTOSC is stable
0 = HFINTOSC is not stable
bit 1 LTS: LFINTOSC Stable bit (Low Frequency – 31 kHz)
1 = LFINTOSC is stable
0 = LFINTOSC is not stable
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In the PIC16F886.h header file it has this:
| Quote: | #define OSC_STATE_STABLE 4
#define OSC_31KHZ_STABLE 2
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So, the bit is used to determine when the oscillator has stabilized after a
startup or frequency switch.
You don't have to worry about it or do anything. When the
"setup_oscillator" statement is executed it will test the HFINTOSC bit and
wait until the oscillator is stable before continuing.
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Google and Forum Search are some of your best tools!!!! |
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bkamen
Joined: 07 Jan 2004
Posts: 1615
Location: Central Illinois, USA
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| Posted: Sat Aug 04, 2012 11:24 am |
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Definitely read the section of the datasheet for your PIC a few times (soak it in) about the Oscillator... I did a few times and then experimented to make sure it was doing what I wanted.
I did an 18F46J11 project that switched between 10 and 40 MHz -- worked swell.
Had to deal with change in delays and baud rates -- but all was good once all those factors were accounted for.
-Ben
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