Re: MSP430 External Clock
From: Tsvetan Usunov (tusunov_at_my-deja.com)
Date: 03/02/04
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Date: 1 Mar 2004 23:33:28 -0800
Mike Page <mike@SCRUBeclectic-CAPSweb.BLAMEco.SWENuk> wrote in message news:<1078172777.266919@ananke.eclipse.net.uk>...
> Hi All,
>
> On any other chip external clocking would be a very simple thing, but
> not on the MSP430F437 it seems. Has anyone managed to externally clock
> XT1 with 32kHz (or thereabouts ?) I am having trouble with the chip
> giving me LFOF and shutting off ACLK (which is the whole reason for
> clocking XT1 - I'm using the LCD). Works just fine with a watch crystal,
> but I want to dispense with it and use an external 4060.
>
> For technical reasons I can't use just XT1 and the FLL. The DCO
> generates too much PWM jitter for my application. And for unknown
> reasons the LCD drive is quite inflexible in its choice of clock source,
> so I can't just hook my X MHz crystal up to XT1 either.
>
> TIA,
> Mike.
Hi,
we have the same problems with MSP430F449 boards, the 32kHz oscillator
is very high impedance and all problems are mostly caused by not good
cleaning of the PCB after soldering (we changed also our PCB routing 3
times until we make it less sensitive).
If your oscillator is not starting just re-clean the PCBs, after that
try to avoid finger tip touching around 32kHz crystal area, board
which works ok stop after you touch the 32 kHz oscillator with finger
and start working again after clean it!
F44x series are with the worse oscillator circuit from the whole
MSP430 family all other members have no such problems
you can check Texas Instrument's PCB crystal layout recommendations
for MSP430 family which is on our web site:
http://www.olimex.com/dev/pdf/MSPPCB.pdf
another software "patch" of the problem is to run timer to do
interrupts with some frequency and to toggle LCD clock inside
interrupt routine, but this will increase your power requirements for
the application as you will frequently wake up the uC with the timer
interrupts
Best regards
Tsvetan
--- PCB prototypes for $26 at http://run.to/pcb (http://www.olimex.com/pcb) Development boards for ARM, AVR, PIC, and MSP430 (http://www.olimex.com/dev)
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