How to check the K555LA13 chip?

Question

Iron

There is a K555LA13 chip. I'm trying to check it, i.e. how it reacts to the supply of "1" and "0", but for some reason it behaves like an OR-NOT element, although it is an NAND element, tell me how to check it correctly, maybe I'm doing something wrong?

Normally, the inputs are zero (nothing is connected) and the LED lights up as soon as I apply 1 to one of the inputs or both inputs, i.e. 3.5V, then the LED goes out, which is typical of the OR-NOT element.

Answer 1

If the input of the K155 and K555 series microcircuits remains free, then, according to the circuit diagram of the element, this is equivalent to the presence of a logical “1” level on it.