Thanks everyone, I'm going to try out the NXP PFC2123 with SPI.  No =

integrated crystal, but <$1 @ 100pcs via digikey.

Tony

Isaac Marino Bavaresco wrote:
> Harold Hallikainen escreveu:
>   =

>> I agree with you. For simplicity and cost, it really seems worthwhile to
>> just use an external RTC chip. Most of them seem to be I2C, but I like S=
PI
>> better (faster, simpler, etc.). There are some RTC "chips" that have the
>> crystal and temperature compensation on board. You can really accurate
>> that way.
>>
>> Harold
>>   =

>>     =

>
> I agree with both. I like to use Maxim-Dallas' devices, but I prefer the
> I2C ones because they use less I/Os and I can share the bus with other
> devices without using more I/Os for chip selects.
>
>
> With SPI you will need 3 I/Os plus one I/O per device in the bus. Indeed
> SPI is faster (up to several Mbps) and I2C is usually 400kbps (some
> devices work up to 1Mbps) but unless your PIC is using a very high clock
> you won't be able to break the 400Kbps barrier with bit-banged SPI or
> I2C anyway.
>
> And on the simplicity subject, after you have a well written set of
> routines to deal with the communications, the complexity/simplicity
> stays hidden.
>
> Regards,
>
> Isaac
>
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