Recently I have been looking over some very old TTL data, and found a term that is new to me - a TRIdirectional Bus. I was unable to find a definition (one of the few times Google has failed me). From what I can gather, the term is not a misprint (it appears in too many datasheet specs) and is NOT someone's idea of what a TRI state output may be (I have found specs that suggest devices made for TRIdirectional busses can also be Tristate devices). So, I ask you - what is a TRIdirectional bus? Thanx.

 

Recently I have been looking over some very old TTL data, and found a term that is new to me - a TRIdirectional Bus. I was unable to find a definition (one of the few times Google has failed me). From what I can gather, the term is not a misprint (it appears in too many datasheet specs) and is NOT someone's idea of what a TRI state output may be (I have found specs that suggest devices made for TRIdirectional busses can also be Tristate devices). So, I ask you - what is a TRIdirectional bus? Thanx.

Could be an attempt to skate around NatSemi(?)'s trademark "Tri-State"

 

what is a TRIdirectional bus?

Never heard of it. Can you post a reference so we can see the context in which it's being used?

 

Is the book referring to TriState Buss, bi directional when active, floating
HiZ when in TriState ?

Regards, Dana.

 

The only reference I found is a SN74LS442 chip, which acts as a sort of bridge that enables three chips to communicate with each other. Not very usual or useful IMO.

 

The only reference I found is a SN74LS442 chip

Do you have a link to a datasheet? I couldn't find one...

 

Do you have a link to a datasheet? I couldn't find one...

Try this link for an HCMOS version of the part. It is described as a "quad Tridirectional Bus Transceiver" and has three 4-bit ports. A two-bit input selection code selects which of the ports is to be used as an input, and three output-enable pins select which port or ports the selected input will be transferred to.

The chip itself is "tridirectional" only in that it interconnect its three ports in any input/output configuration; as for a "tridirectional bus" per se, I don't believe there is any such thing.

 

Hello,

@dl324 , here is the datasheet

Bertus

 

Never heard of it. Can you post a reference so we can see the context in which it's being used?

The context was merely an attribute listed in a few datasheets, with no further comments. I was researching some old parts in my stash when I saw these references in several old online databooks (which, of course, I can't find again).

 

Is the book referring to TriState Buss, bi directional when active, floating
HiZ when in TriState ?

Regards, Dana.

The Datasheets in question did not elaborate, so your guess is as good as mine as to the intent.

 

The only reference I found is a SN74LS442 chip, which acts as a sort of bridge that enables three chips to communicate with each other. Not very usual or useful IMO.

Thanx for that tip! At least that is more info than I had found so far. So it sounds like these things are similar to ganged data selectors maybe, with open collector outputs available??? Thanx again!

 

Do you have a link to a datasheet? I couldn't find one...

https://pdf1.alldatasheet.com/datasheet-pdf/view/28015/TI/SN74LS442.html

 

Try this link for an HCMOS version of the part. It is described as a "quad Tridirectional Bus Transceiver" and has three 4-bit ports. A two-bit input selection code selects which of the ports is to be used as an input, and three output-enable pins select which port or ports the selected input will be transferred to.

The chip itself is "tridirectional" only in that it interconnect its three ports in any input/output configuration; as for a "tridirectional bus" per se, I don't believe there is any such thing.

It is now becoming clearer and clearer.... Thanx!