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H4 Fuse with External Oscillator on 18f14k22 way off!

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evsource

Joined: 21 Nov 2006
Posts: 129

H4 Fuse with External Oscillator on 18f14k22 way off!

Posted: Wed Jul 14, 2010 2:20 pm

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I'm using PCH version 4.092 with a 18F14K22. I've got a 10.000mHz crystal with 18pF capacitors.

The following, as verified on a scope, gives about the right timing (seems to be about 12us instead of the expected 10, but in the ballpark at least):

Code:

#include <18f14k22.h>

#fuses HS,WDT256,NOMCLR,NOWDT,NOBROWNOUT,BORV22,NOLVP
#fuses NOPROTECT,NOCPD,NOCPB,NOWRT,NOWRTD,NOWRTB,NOWRTC,NOEBTR,NOEBTRB

#use delay(clock=10000000)

void main() {
while(1) {
output_low(PIN_C1);
delay_us(10);
output_high(PIN_C1);
delay_us(10);
}
}

But when I try to get 40mHz out of it with the following code, the pulse takes 400us! Exactly 40 times what it should.

Code:

#include <18f14k22.h>

#fuses H4,WDT256,NOMCLR,NOWDT,NOBROWNOUT,BORV22,NOLVP
#fuses NOPROTECT,NOCPD,NOCPB,NOWRT,NOWRTD,NOWRTB,NOWRTC,NOEBTR,NOEBTRB

#use delay(clock=40000000)

void main() {
while(1) {
output_low(PIN_C1);
delay_us(10);
output_high(PIN_C1);
delay_us(10);
}
}

Is this a compiler bug? Could someone compile this code with a newer version and PM the hex file to me so I can try it?

PCM programmer

Joined: 06 Sep 2003
Posts: 21708

Posted: Wed Jul 14, 2010 3:18 pm

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Edit your 2nd program:

1. Change the H4 fuse to HS.

2. Add this line to the beginning of main():

Code:

setup_oscillator(OSC_PLL_ON);

evsource

Joined: 21 Nov 2006
Posts: 129

Posted: Thu Jul 15, 2010 4:19 pm

Reply with quote

PCM programmer wrote:

Edit your 2nd program:

1. Change the H4 fuse to HS.

2. Add this line to the beginning of main():

Code:

setup_oscillator(OSC_PLL_ON);

Ah, okay, thanks. Who would have thought?!

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