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'[PIC]: Possible PLL problem with 18f452?'
2004\03\05@090304 by Joe Jansen/TECH/HQ/KEMET/US

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bah...   fixed the subject line.....


----- Forwarded by Joe Jansen/TECH/HQ/KEMET/US on 03/05/2004 08:59 AM
-----

Joe Jansen/TECH/HQ/KEMET/US wrote on 03/05/2004 08:59:02 AM:

{Quote hidden}

enabled:
> >
> > >You do know that the PLL on/off setting takes its (new) effect only
> > after a power down - power up?
> >
> > Yes I do, I found out the hard way the first time I tried to use it
:-)
> >
> > Each time I enable or disable the PLL I remove power and then
reaply...
> >
> > Also I discovered another problem I can't figure out. The following
code:
{Quote hidden}

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2004\03\05@131825 by Joe Jansen/TECH/HQ/KEMET/US

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Thinking about your code some more, you could re-write it as follows,
which would only add 1 clock/memory word for the final NOP before the e1
loop.  However, in a real app, you probably have something else to do
after you send out that final character (like load something else into w),
which you could start, and check that the character went out sometime
later.


<code>

  movlw 'T'
  movwf TXREG
  movlw 'e'
a1:  btfss PIR1, TXIF
  goto a1
  movwf TXREG
  movlw 's'
b1:  btfss PIR1, TXIF
  goto b1
  movwf TXREG
  movlw 't'
c1:  btfss PIR1, TXIF
  goto c1
  movwf TXREG
  movlw '-'
d1:  btfss PIR1, TXIF
  goto d1
  movwf TXREG
  NOP
e1:  btfss PIR1, TXIF
  goto e1

</code>

HTH!

--Joe Jansen



pic microcontroller discussion list <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU> wrote on
03/05/2004 08:46:19 AM:

> >> I'm experiencing strange behaviour with the 452 and the PLL enabled:
>
> >You do know that the PLL on/off setting takes its (new) effect only
> after a power down - power up?
>
> Yes I do, I found out the hard way the first time I tried to use it :-)
>
> Each time I enable or disable the PLL I remove power and then reaply...
>
> Also I discovered another problem I can't figure out. The following
code:
{Quote hidden}

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2004\03\05@135802 by Jan-Erik Soderholm

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Hi.
Another way of handling this (sending multiple bytes/characters
out on the UART line), is to implement a FIFO buffer where
the characters to be sent are written, and a UART TX-ISR that
are fetching from the FIFO (as long as it isn't empty) and
writing them to the UART TXREG. Thay way, your main code
doesn't have to wait until your FIFO buffer is full. Most of the time,
the FIFO can be sizes so it never will be full.

For an example (not the easiest to read, but works out-of-the-box)
is Olins UART routines found on http://www.embedinc.com/pic. The UART
routines are "embeded" into the include files, so you have to
look araound a bit...

Regards,
Jan-Erik.

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