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Multiplexing Clock on 8051 type uController

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

Reply to
Jim Stockton
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"Jim Stockton" wrote

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:

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The proper datasheet (etc) for this part:
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Reply to
Apollo

Apollo schrieb:

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.
http://www.autometer.de

==================================================================
In a world without walls and fences, who needs Windows and Gates ?
(Sun Microsystems)
Reply to
Tilmann Reh

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

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Reply to
Apollo

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

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or
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Cheers, Schwob

Reply to
Schwob

Schwob schrieb:

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.
http://www.autometer.de

==================================================================
In a world without walls and fences, who needs Windows and Gates ?
(Sun Microsystems)
Reply to
Tilmann Reh

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