Multiplexing Clock on 8051 type uController

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I am looking at muxing the clock to save power on an 8051 type
controller.
Has anyone had any experience with that. During standby period I need a
real time clock and to occaisionally monitor sensors. I think a 32.768
KHz clock will work fine for this. At the appropriate time I need a
higher speed clock to run the calculations and communications. Don't
tell me about the 430 I know it is probably ideal but I don't have time
or tool chain that it would take. There is also a PIC slave processor
that is only clocked during the high speed phase. Any thoughts.
Jim Stockton

Re: Multiplexing Clock on 8051 type uController
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P89LPC932 is an 8051 derivative that has this feature built in -
You can multiplex between an external crystal at 32.768khz and the
internal trimmed RC oscillator (+/-2.5%) 7.3728Mhz.  Actually, you
can also Mux between an internal 400khz oscillator, and do other
stuff as regards dividing the clock - but you did not ask for any
of that...
My comments on this part:
http://www.airborn.com.au/8051/isp.html
The proper datasheet (etc) for this part:
http://www.semiconductors.philips.com/pip/P89LPC932.html




Re: Multiplexing Clock on 8051 type uController
Apollo schrieb:

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Yes, that's a very nice and powerful chip.
However, there still are some bugs. Especially dividing the clock
has some interesting side effects (not mentioned in the errata sheet
yet, but I found two bugs during the last few weeks).
But since it also has an RTC counter, switching the clock would
be possible without losing time accuracy.

--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
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Re: Multiplexing Clock on 8051 type uController

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Yikes.  I can't say I have actually used these clock switching
features yet.  I'll watch the errata sheets (or be careful when
I DO use those features)

Steve
www.airborn.com.au




Re: Multiplexing Clock on 8051 type uController
Hi all,

Errata Sheets do cover these problems of dividing the clocks and they
are related to the CCU (Capture Compare Unit) only. If the CCU runs at
full speed and that's the way most people use it, no problems! For
clock dividing to reduce power, and I guess that was the original
question, no problems.
Depending on your I/O needs and schedule, you might want to look at
the LPC92x (20-pin 2-8k flash), the LPC91x (14-pin, 1k flash) or even
LPC90x (8-pin, 1k flash).
A very nice inexpensive ($59) evaluation board is available through
www.keil.com or www.philipsmcu.com

Cheers, Schwob

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Re: Multiplexing Clock on 8051 type uController
Schwob schrieb:

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No.

I explicitly mentioned that these bugs are *not* mentioned in
the errata sheet yet, and I didn't mention the CCU either.

--
Dipl.-Ing. Tilmann Reh
Autometer GmbH Siegen - Elektronik nach Maß.
We've slightly trimmed the long signature. Click to see the full one.

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