High Z in io port
- Thread starter Alex1700
- Start date
no, i want to know what is the high-impedance state
hi Alex,
When both output MOSFET's are Off, ie: non-conducting.
Usually referred to as Tri-state devices.
E
https://www.electronics-tutorials.ws/logic/logic_9.html
Clip: from link.
When both output MOSFET's are Off, ie: non-conducting.
Usually referred to as Tri-state devices.
E
https://www.electronics-tutorials.ws/logic/logic_9.html
Clip: from link.
what is the use of a tristate device?
No
In computer systems IC just uses 5v power, it will have a loading effect?
After reading the link you share right now I have a better understanding of high Z and tristate buffer thanks bro
drjohsmith
- Joined Dec 13, 2021
- 852
In days of old,
( the 8051 is what 40 plus years old )
Digits were great big 5v logic
( a step down from the 12 v logic I started with )
Things were parallel,
if you wanted to send 16 bits from a to b, you used a 16 bit single ended bus,
If that bus was one direction,
say form CPU to an output, that works great,
the CPU can drive the bus all the time,
But what if you want if you wanted two things to send data out,
then if both were on the bus driving all the time, then you would end up with a conflict,
say one bit was being driven high by one driver, and low by the other !
This where tri state comes in,
it enables a device to "stop driving the bus"
its a very high impedance, and resistively a minimal load,
This also allows a device that is in tri state, to listen to the bus,
i.e and input .
This is how buses as S100, PCI and ISA worked.
Not used so much now days,
buses are serial, and point to point, such as PCIe,
The 8051, had one port that had real drivers, up and down,
the other ports, were what wed now call open collector,
a pull down, needing a pull up on the board to make a high,
( the 8051 is what 40 plus years old )
Digits were great big 5v logic
( a step down from the 12 v logic I started with )
Things were parallel,
if you wanted to send 16 bits from a to b, you used a 16 bit single ended bus,
If that bus was one direction,
say form CPU to an output, that works great,
the CPU can drive the bus all the time,
But what if you want if you wanted two things to send data out,
then if both were on the bus driving all the time, then you would end up with a conflict,
say one bit was being driven high by one driver, and low by the other !
This where tri state comes in,
it enables a device to "stop driving the bus"
its a very high impedance, and resistively a minimal load,
This also allows a device that is in tri state, to listen to the bus,
i.e and input .
This is how buses as S100, PCI and ISA worked.
Not used so much now days,
buses are serial, and point to point, such as PCIe,
The 8051, had one port that had real drivers, up and down,
the other ports, were what wed now call open collector,
a pull down, needing a pull up on the board to make a high,
DickCappels
- Joined Aug 21, 2008
- 10,180
A pin in a high impedance state might be an input of merely disconnected from the external circuit. That is the third state beyond Low and High - why it is called tristate.
It should really be referred to as three-state, not tri-state. The term tri-state is a registered trademark of National Semiconductor (now part of TI). However, I think that it is considered dead and non-revivable by the USPTO (but since TI continues to use it, they have common-law rights to it and, legally, no one else can use it for the same purposes). Having said that, I suspect NS (and now TI) have long since given up trying to defend it.
I think you missed the announcements from NS about 30-years ago (early 1990s) when they said their failure to enforce and protect their trademark caused several to become a standard term of commerce so they elected not renew those trademarked terms - including Tri-state. TI never had anything to do with the decision.
Yes, I missed that. The trademark (0941335) expired in '93 and was not renewed at that time, but NS did file a renewal in '97 that was granted (2138646) and then renewed in 2007 for an additional ten years, meaning that it was transferred to Texas Instruments when they bought NS in 2011. The trademark was not renewed in 2017 (which would have been a TI decision) and was administratively cancelled in 2021 by the USPTO. It's status under common-law can really only be determined if tested in the courts by someone else attempting to trademark it.
Thanks for looking that up. Did they get the new Trademark for a circuit input or for the Pennsylvania, Ohio, West Virginia invitational basketball tournament?
For "integrated circuits and data sheet manuals sold as a unit therewith".
