regenerating the CPU clock (ex tiny 26)

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#1
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Hello:

I am using an attiny 26 with an external 10Mhz crystal. I need the stability of a crystal, but don't want the cost of an oscillator module (unless there is one in the 80 cent range). However, I need to use the 10Mhz elsewhere on the circuit board...Is there a way to spit the 10Mhz out of one of the processor pins?

I know some of the MEGA devices have a fuse that can be set for this purpose. I was thinkning perhaps one of the timers or the peripheral clocks could be redirected straight out one of the port pins.

I have already tried connecting a cmos gate to one of the crystal pins. Unfortunately there is only about 1V of swing--not engough to do a good job of driving the gate. THe PIC parts seem to be able to do this since they swing almost a full 5V. Can the tiny26 be set to swing (drive) the crytal harder?

I thank you profusely in advance for your wise council.

Hoyt

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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Yes, simply set the fuse to "full logic level" clock and take the signal from the output pin of the oscillator. I can tell you that the low-amplitude clock makes it MUCH easier to meet FCC/CE emissions tests!

I should add that this is "generic" information. I have no first-hand experience with a Tiny26.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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The Tiny26 CKOPT fuse seems to work differently. The datasheet specificaly says not to set CKOPT with a crystal.

Ralph Hilton

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By putting the crytal in the "high power" mode, I'm assuming you mean setting th eckopt bit.

I tried it and it worked well!! Thankks.

As for the postabout not setting the bit, I initially saw this and did not set the bit for this reason. but if you re-read the sheet (in section Crystal Oscillator, pg 25) the previous sentence is referring to a resonator. "The CKOPT fuse should always be unprogrammed when using this clock option". So the writing leaves me a bit confused too.

I can't find anything in the datasheet denoting any difference or way of changing from low to high power crystal drive, but this pin does seem to. Any info would be appreciated.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!