How not to leave ISP reset floating?

Question

I have read that it is inadvisable to leave the reset pin on an MCU floating, also I would like to expose the pins of my ATtiny84 so that it can be programmed by an Arduino. Is the 10kΩ resistor in the below schematic the correct way to tie reset to ground, while still allowing the MCU to be programmed via ISP?

schematic

^{simulate this circuit – Schematic created using CircuitLab}

Thank you, I missed that when asking the question. So I assume I just need it the other way round, i.e. the resistor connects to Vcc? — Morgoth, Apr 25 '21 at 08:29

score 3 · Accepted Answer · answered Apr 25 '21 at 09:59

The ATtiny84 already has an internal pull-up in the order of 50 kilo-ohms, so you really don't need to connect any external components at all.

If you really want to be on the safe side, for example in environment with high electromagnetic interference, you can use an external 10k pull-up if you want.

There is also a hardware getting started application note available which explains best practices how to connect the reset pin under various situations, for example if you are going to use DebugWire or not, or want an external reset button.

Enrico Migliore · Answer 2 · 2021-04-25T12:32:49.663

-2

Your microcontroller, to work properly, needs at runtime a high logic level on the RESET input pin.

That means that you have to tie R1 to VCC and not to ground.

edited Apr 25 '21 at 12:32

answered Apr 25 '21 at 09:00

Enrico Migliore

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Yes, except all the ones that need active high reset. – Justme Apr 25 '21 at 09:47

How not to leave ISP reset floating?

2 Answers2