Multiplexing Clock on 8051 type uController

"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:

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.

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

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

Cheers, 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.