Open collector to MCU input pin

If an external reset is desired, the signal must be either open collector or open drain without
any form of pullup. Do not pull this line high with either a pullup or a driven logic one. When
this line is pulled low, the module will immediately drop into hibernate mode with some loss
of data. When the external reset is released, the module will go through its normal power up
sequence provided the VDD supply is within specifications.

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alexan_e said:

I don't understand why there a need for an explanation in order to follow what the manufacturer suggests

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bigdogguru said:

I would also like to add, posting a single quote out of context from the datasheet makes it difficult to determine the reasons.

It is not clear, from the quote alone, the specific purpose of this "line."

You would be much better served to always include a link to the specific datasheet from which the quote originates.

Or at the very least specify the manufacturer and model number of the device to which it refers.

BigDog

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bigdogguru said:

I would also like to add, posting a single quote out of context from the datasheet makes it difficult to determine the reasons.

It is not clear, from the quote alone, the specific purpose of this "line."

You would be much better served to always include a link to the specific datasheet from which the quote originates.

Or at the very least specify the manufacturer and model number of the device to which it refers.

BigDog

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The JF2 NRESET pin is normally connected to a 0.33uF ceramic capacitor. The JF2 will
generate an internal reset as appropriate. No external reset signal needs to be applied to the
JF2.
If an external reset is desired, the signal must be either open collector or open drain without
any form of pullup. Do not pull this line high with either a pullup or a driven logic one. When
this line is pulled low, the JF2 will immediately drop into hibernate mode with some loss of
data.

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alexan_e said:

So the manufacturer gives that direction because an external pullup or strong drive will interfere with the internal reset circuit

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I don't have a reference.

The value of a pullup must be high enough for the driver to be able to pull it down.
The manufactures has already included such a resistor internally (it seems so) and has an appropriate internal pull down switch , if you add another external pullup then the internal switch will have to sink more current and it may not be able to.

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Good advice, though there also might be a reason for them to write it (maybe for fun, or maybe due to some MCU structure, I'm not aware of...). I wouldn't bother writing there if I wasn't interested in that cause...

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