32kHz osc. on ATmega103L

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Hi,

I just got some samples of ATmega103L. What I would like ask you, is some questions about the 32kHz oscilator circuit.

1) When I don't use the oscilator, should I connect the input pin TOSC1 to GND?

2) Can I take the signal from TOSC2 when the oscilator runs, as a clock for other circuits via an buffer like HC14 or simple FET?

3) Works the circuit o.k. without any usual components like 2x C to GND and R between the two pins and could this components make the oscilator working more stable?

I didn't found any comments on this in the datasheet.

Thank you for your answers and tips.

Andrej

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Hi Andy,

1.
The TOSC1/TOSC2 pins don't have any secondary purpose as general I/O. Because of this, the normal leakage current you get from the input buffer will not appear. If your concern is ESD protection, you would benefit from connecting TOSC1 to GND. Make sure to leave TOSC2 N/C, as the two pins are connected through a resistor.

2.
No, the TOSC1/TOSC2 signal is to weak. Use the XTAL1/XTAL2 output instead if you can.

3.
You don't need a resistor between the pins, nor external decoupling capacitors. This has been implemented internally.

Best regards,

Morten, AVR tech. support.

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Hi Morten,

thank you for your answers. It helps me.

The idea to use the signal from TOSC2 was the same as from XTAL2 but with lower frequency. I would like to say, that this could be possible via an FET, but I don't have the time to test it now. I connect the crystal without any external components and place one jumper to GND on TOSC1 for the case without crystal.

Andrej

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