You have defined OSC 8; is the crystal actually 8? If you dont define this 
(use the default 4 MHz) does the frequency double?

Also, the LED would be on for 1 second, and off for 1; the cycle would be 2 
seconds.

Regards,

Anand

----- Original Message ----- 
From: "Mark Wotton" <mwotton@gmail.com>
To: <piclist@mit.edu>
Sent: Sunday, September 03, 2006 7:46 PM
Subject: [PIC] time-scaling problem with PIC 18F2455


> Hello,
>
> I'm trying to program a PIC 18F2455 chip. I'm using PicBasic Pro as a
> frontend, MPLab v7.30 for the assembler, and MPLab icd 2 for the
> programmer. A simple testing program to flash a light on and off at 1
> second intervals instead takes 8 seconds:
>
> ----------------------------------------
> INCLUDE "modedefs.bas"
>
> define OSC 8
>
> TRISA=%00000
> TRISB=%00000000
> TRISC=%11111111
>
> StatusLED VAR porta.1
>
> LOOP:
>  high StatusLED
>  pause 1000
>  low StatusLED
>  pause 1000
>  goto LOOP
> ------------------------------------------
>
> If I change OSC to 4 (or leave it out), the program takes 4 seconds
> per transition, so I initially thought I could just set OSC to 1 and
> be done with it - this wouldn't compile in PicBasic Pro, however,
> giving me the error "Symbol not previously defined (PAUSEUSL)".
>
> I tried fiddling with some of the constants defined in
> C:\pbp\p18f2455.inc, which the generated assembly included:
> --------------------------------------------
>   INCLUDE "P18F2455.INC"  ; MPASM  Header
>        __CONFIG    _CONFIG1L, _PLLDIV_5_1L & _CPUDIV_OSC1_PLL2_1L &
> _USBDIV_2_1L
>        __CONFIG    _CONFIG1H, _FOSC_HSPLL_HS_1H
>        __CONFIG    _CONFIG2H, _WDT_ON_2H & _WDTPS_128_2H
>        __CONFIG    _CONFIG3H, _PBADEN_OFF_3H
>        __CONFIG    _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L
> ---------------------------------------------
>
> Unfortunately, nothing there seemed to have any effect on the timing
> at all. Where do you suggest I look next? I'm at a bit of a loss.
>
> (It's important that the timing be right for this, as I need to use
> serial comms to load new data at runtime, and SERIN doesn't seem to
> want to work, even when I tried setting the baud rate on the other end
> of the serial to 1200 to compensate.)
>
> Please let me know if I've missed describing anything important, I'm
> still quite new to PIC programming.
>
> Cheers,
> Mark
>
> -- 
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> 

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