I been asked by a non-technical friend about USB, and I couldn't think of the reason why a set of wires is called a "bus". Anyone know why? or the history behind ?
Joe
I been asked by a non-technical friend about USB, and I couldn't think of the reason why a set of wires is called a "bus". Anyone know why? or the history behind ?
Joe
There are many things like that. Even the common now words like bug, driver and bit have different meaning when it comes to engineering. There's always some history or at least coincidence behind.
Alex
Joe wrote in news:ck49st$i1t$1$8300dec7 @news.demon.co.uk:
Typically it's called a "bus" when more than one device (well, really more than two to exclude dedicated point to point connections) can be attached to it. So it's a "bus" when multiple devices share the same set of wires to communicate. USB fits such a definition.
-- Walter Mallory walter.mallory@mbda-us.com Reach, Connect, Celebrate, Grow, Serve
I don't know the history, but when I was just a young grasshopper, I asked the same question to my engineering mentor. He says if you've got 16 people and you need to take them all to the same place at the same time, how would you get them there ? You would put them on a bus.
Probably comes from electrical power distribution - bus bars have been around for a very long time, certainly from before computers were developed. The term probably came from buses used for transportation, they were originally horse-drawn.
Leon
The electronic 'bus' will be derived from the electrical 'bus-bar', which has been around for ~100+ years. Just why the Electrical pioneers used 'bus-bar' - who knows. Perhaps it literally buzzed in use -> buzz-bar -> bus-bar ? :) Or maybe a brand-name morph, of an early supplier ?
-jg
Really ? I thought that you always have a hub between. So only two devices on the same cable, which is then point to point ...
In USB, it's only a "bus" _logically_. Physically, it's a network of point-to-point connections, not a bus.
FWIW, even a single wire carrying power can historically be called a "bus".
-- Grant Edwards grante Yow! I just forgot my at whole philosophy of life!!!
From the Howe dictionary:
The term is almost certainly derived from the electrical engineering term "bus bar" - a substantial, rigid power supply conductor to which several connections are made. This was once written "'bus bar" as it was a contraction of "omnibus bar" - a connection bar "for all", by analogy with the passenger omnibus - a conveyance "for all".
-- Al Balmer Balmer Consulting
developed.
From
The term is almost certainly derived from the electrical engineering term "bus bar" - a substantial, rigid power supply conductor to which several connections are made. This was once written "'bus bar" as it was a contraction of "omnibus bar" - a connection bar "for all", by analogy with the passenger omnibus - a conveyance "for all".
More on derivation
"E.S." wrote in news:%Si9d.142$ snipped-for-privacy@fe39.usenetserver.com:
You do need a hub, but they are sharing the bandwidth (or the communication channel if you like). I also look at the hub as being nothing more than a signal repeater/buffer. And there's still only the one USB controller (master) (even if there is a fan-out of multiple hubs and devices). I think what I said before is still basically accurate: but something like USB starts to blur the concept of a bus a bit.
Plus I got the distinct impression after posting (and reading a few other posts) that the OP was curious as to why the word "bus" was used to describe such a thing as opposed to some other word: instead of what technically constitutes a bus.
Wouldn't be the first time I misunderstood someone on usenet. :-)
-- Walter Mallory walter.mallory@mbda-us.com Reach, Connect, Celebrate, Grow, Serve
Grant Edwards wrote in news:4165bb9c$0$55252$a1866201 @newsreader.visi.com:
I don't think it's really a network of point-to-point connections either, because no signal switching is occuring. Maybe saying that it's a communications bus but not an electrical bus might be more accurate. Come to think of it, that's just what you said, isn't it? I think we're in violent agreement.
"It's a floor wax *and* a dessert topping!"
True.
-- Walter Mallory walter.mallory@mbda-us.com Reach, Connect, Celebrate, Grow, Serve
In Durham, North Carolina, the city runs busses emblazoned with the acronym of the agency on the side: Durham Area Transit Authority. It's the largest DATA bus I've seen to date, with excellent driver support and very few crashes.
Ed
Thanks guys for all the answers :-)
Joe
driver
always
LOL. Is it collision detect or collision avoid? :-)
I'd say it's just the other way around. For the power wires, it is a bus but not for the data. Or does every slave see the data to an from every other slave (haven't browsed the standard for a while)?
Meindert
driver
always
You made me laugh. :) Great!
Alex
-------
Also, in 11.1.2.1 it says that a USB hub (the repeater part) acts as a switch. Is sends data from the upstream port to all downstream ports, but data from a downstream port is only sent to the upstream port, all other USB slaves do not see the reply from one slave.
So.... USB is not a bus.....
Meindert
Is this bus synchounous or a-synchronous? Buffered? What is its latency? 10 minutes? ;-)
Generally, a bus is a medium designed to transport data in more than one direction over relatively short distances. Think of pcb's in this case, just to avoid confusion with networks.
Waldemar
"Meindert Sprang" schreef in bericht news: snipped-for-privacy@corp.supernews.com...
either,
USB
No? What does USB stand for? UNIVERSAL SERIAL BUS... As I stated before, generally a bus is a medium designed to transport data back and forth between at least two devices. Whether it is serial or parallel, whether it has hubs, buffers, etc. is of no relevance whatsoever. Nor is the way in which devices connected to the bus communicate. BUS is just a generic term.
Waldemar
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