High Output Impedance State in Processors: What Does It Mean and When Is It Used?

Hello, maybe someone will explain to me what is the state of high output impedance in processors

Hello
The high impedance state is third after the low and high levels. In this state, the output behaves like an input, i.e. it does not load the line to which many other outputs can be connected, but only one can be active at a time. When you connect a lot of RAM and the outputs are connected together, you can only read the memory content from one cube and the other ones are in a high impedance state.

ok, as I understand it, the high impedance state is a state in which any system working on the bus is waiting for the next transmission

qwerty1 wrote:

ok, as I understand it, the high impedance state is a state in which any system working on the bus is waiting for the next transmission

No, because the output is waiting for nothing, as it could be described, the output in the HiZ state (because this is also how the high impedance state is also called) is "hidden" and then the system pretends that it is not really there ... .
A similar thread was already there:
https://www.elektroda.pl/rtvforum/topic70376.html

qwerty1 wrote:

ok, as I understand it, the high impedance state is a state in which any system working on the bus is waiting for the next transmission

Not. A high impedance state is one that "simulates" the physical disconnection of a system from a connection, such as memory from the data or address bus. This is actually a "third" logical state. High state, low state and hi-z state, which does not affect the state of what is connected to the system.

If you have several systems connected e.g. in a data bus, it is obvious that you do not want to read them all at once, only one at a time (except in justified cases, of course ). Meanwhile, what appears at the output of such a data bus is a logical sum on the wire - a low state on at least one system would determine the state of the entire data bus. This, of course, makes it impossible to read a particular system, because other systems "interfere".

And this is where the high impedance ("hi-z") state can be applied. If you put all the circuits except the read one into this state (specifically their outputs) then they are in the state as if they were disconnected from the one you are interested in and they stop "disturbing" it because they have no influence on its outputs. Hmm is it understandable?

m8se wrote:

This is actually a "third" logical state.

I would disagree with that. There is no logical state called high impedance. There are logical states of low, high, and a state in which the signal is contained in the forbidden band (the voltage range from the maximum low-state voltage and the minimum high-state voltage.Bypass for the standard family of TTL circuits is in the range 0.8V-2.0V) . The output of the system can either be active, when its presence affects the state of the line it is connected to (i.e. the voltage level on it), or in a high impedance state, when it does not affect the voltage on the line connected to it. exit.

Just such a small correction not to spread disinformation.

Added after 2 [minutes]:

qwerty1 wrote:

ok, as I understand it, the high impedance state is a state in which any system working on the bus is waiting for the next transmission

This state was formerly known as bus disconnect. It has nothing to do with what the system "is going to", "wait" or "go to sleep". For some reason, he disconnected internally from the bus to which his outputs were connected, and that's it.

I know it, but the fact that I cannot translate and convey knowledge and someone may not understand me as if I was going to.

On the other hand, the high impedance state is in many applications treated as a logical state, e.g. in apparatuses for the decomposition of logic functions intended for programmable logic circuits.

m8se wrote:

I know it, but the fact that I cannot translate and convey knowledge and someone may not understand me as if I was going to.

Welcome to the team, I have exactly the same. :-)

m8se wrote:

On the other hand, the high impedance state is in many applications treated as a logical state, e.g. in apparatuses for the decomposition of logic functions intended for programmable logic circuits.

Since my colleague does not know what high impedance is, he does not need to obscure the image of the world with such "nubs" as devices that decompose logical functions. He will slowly come to whatever he wants.

Regards.

Wind. The high impedance state is in practice a foot hanging in the air. It couldn't be easier ;)

greetings.

Hello
The leg hanging in the air is more NC, don't mix it up unnecessarily.

thank you all for your help, I could not answer earlier because the computer fell, but it's okay, I will have many more questions again, thanks