Re: What's the tri-state? Why to use the tri-state in design
I guess by now everyone must be sure what Tri-state is.
Just to be simplified see it as a valve which do not let the fluid (current in our case) flow from one side to other. So the line connected to the output side of the tri-state buffer is basically floating or high impedance state.
This is the link given by echo47 which clarifies all your doubt that you might have
**broken link removed**
Now the last bunch of quries were about if it has a drive capability. Yes sure it does.
Just like any other buffer Tri-state has a driving capability with the added functionality of being able to achive high impedance at its output when required(i.e when disabled)
If you wish to know whats inside it check the ckt below.
https://www.asic-world.com/digital/gates5.html
Now some were wondering about if we can use it or where we can use it.
1.As Anjali mentioned it is lot of time used near the output pads.
2.Plus it is also used in case of a common bus.Say lot of memory outputs from differnt memories(say 8) driving a single bus.YOu would traditionally like to use a mux.Hower if the width of each of busses is very big say 16 or 32 then the size of the mux will be honking big with inputs at 8x32.So if you want to avoid it emply tristate. But precaution must be taken in the case if you have a condition when nobody is driving the bus then you should have it pulled up.
This is similar to MUX being implemented using TRi-state buffers.
3. Since DC and other tools give errors this is not generally designed at the earlier stage but is included at the layout stages or P&R. Plus there are some testing issues with the tri-states employed on the chip.