Lpc2000

Try using an external STMicro M41T81 RTC.  It interfaces via the I2C bus
and has a multi-function pin (watchdog reset, alarm interrupt, etc.)
It also has a register for calibrating the crystal.  Reasonably low cost
and available from Digikey for $2.40 USD.  Then set the RTC to wake up the
ARM via an external interrupt and put the LPC to sleep.

Regards
-Bill Knight
theARMPatch




On Sat, 15 May 2004 03:43:27 -0400, Milos Prokic wrote:

Hi, thanks on your reply.

Since the RTC is essential for my application, as well as low cost and low
power consumption I was wondering if you know how much power is required to
keep the RTC running? Is that a good approach? If you know approximately
what is the average current consumption if all the peripherals are switched
off except for RTC and the chip is placed in the idle state that would
really be of great help.

Thanks in advance,

Milos 



  _____  

From: philips_apps [mailto:philips_apps@...] 
Sent: Tuesday, May 11, 2004 3:02 PM
To: lpc2000@yahoogroups.com
Subject: [lpc2000] Re: LPC210x RTC



Hello Milos,

The RTC cannot work once the microcontroller enters the power-down 
mode, since there will be no clock supplied through the 
microcontroller and consequently to the RTC block. The only low power 
mode that the RTC user can utilize is the idle mode.

Regards,


--- In lpc2000@yahoogroups.com, "Milos Prokic" <milos.prokic@m...> 
wrote:
> Hi everyone,
> 
> I was wondering if anyone has made use of the RTC module.
> 
> I'm not quite clear from the documentation if the RTC can be used 
during
> powerdown. The doc says that there will be lapse in the time 
update. I'm not
> sure if they mean that this "lapse" results from altering the 
prescaler
> values so that it can get the feed from frequency oscillator and 
not the PLL
> or that it will just stop working until you bring it back from 
power down?
> 
> Thanks a lot,
> 
> m.






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