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How do deal with Input pins, which not in use. Have seen many examples, where they kept floating, but I don't like personally when an high-Z inputs kept floating in the design in some IC which I could not control FW of. Seen DSR, DCD, RI could be tied to DTR if they not in use. Is it ok to tie OSCI to ground via 10 Ohm resistor?

Pinus
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2 Answers2

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but I don't like personally when an high-Z inputs kept floating in the design in some IC which I could not control FW of.

But the datasheet suggests so:

enter image description here

Rohat Kılıç
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First of all, the FT232RL is an old product at sunset stage, now at status of NRND by the manufacturer, so it is not recommended for new designs any more.

Secondly, the datasheet is clear on this, OSCI and OSCO can be left unconnected when not used.

This may be because the external crystal needs to be specifically selected by configuring the chip to use it, so it is possible that the oscillator pins are unused or even disabled when the default internal oscillator is used.

Also the handshake pins that you think are floating because they are unused; the pins are not floating. The datasheet says input pins have built-in 200kohm pull-up resistors to VCCIO.

Justme
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  • thank you for this suggestion, FT234XD do have only signals needed – Pinus Apr 21 '23 at 08:13
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    That silicon chip may be identical to larger devices. It might just be packaged into a 12-pin package badged as FT234 and internally the pins are left disconnected. It is normal to have unused pins left unconnected if the datasheet says it's OK. The golden rule of always connecting unused pins only applies if they clearly can't be left connected, and sometimes ICs have pins that are not connected and you can do anything you like with them, and sometimes they have reserved pins which you must leave open or the part won't work. – Justme Apr 21 '23 at 08:27