OT:why a group of signals is called a bus?

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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


Re: OT:why a group of signals is called a bus?
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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



Re: OT:why a group of signals is called a bus?
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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


Re: OT:why a group of signals is called a bus?

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driver
always

LOL. Is it collision detect or collision avoid? :-)



Re: OT:why a group of signals is called a bus?
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driver
always

You made me laugh. :) Great!

Alex



Re: OT:why a group of signals is called a bus?

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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



Re: OT:why a group of signals is called a bus?
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It's a synchronous bus, according to the schedule.  However, there are
occasional clock synchronization questions.

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Yes.  It's an unusual double-buffer scheme.  I have seen as many as
twelve DATA items waiting to get on the bus.  Then once on the bus,
items are buffered until delivery to their destinations.  Interestingly
each DATA item carries its own routing and destination information,
making it a relatively sophisticated network, which happens to employ buses.

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Average latency at any given point during weekdays is probably around
thirty minutes, but maximum latency is around 13 hours.  Ah, but think
of the bandwidth!  As the old joke goes, "don't underestimate the
bandwidth of a station wagon full of 9-track tapes."  Which is
particularly funny now, because both station wagons and 9-track tapes
are long obsolete...

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That's a good definition, and "relatively short distances" is a good
descriptive detail.  Just to be clear, I think when you say "in more
than one direction" you mean that, for example, the information can go
from a device to multiple other devices, and not that it necessarily has
to be bidirection (i.e. both input and output).  An address bus is a
typical example of this.

Ed


Re: OT:why a group of signals is called a bus?

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I beg to differ regarding station wagons.  They are just as
popular in Europe as ever, and they seem to be undergoing a
resurgence in popularity in the US (several new models
introduced in the past year).  Apparently, some people with
SUVs that guzzle gas and handle like pigs-on-skates have
finally figured out that they never really needed to drive
off-road after all.  ;)

--
Grant Edwards                   grante             Yow!  Jesus is my
                                  at               POSTMASTER GENERAL...
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Re: OT:why a group of signals is called a bus?
@newsreader.visi.com:

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So should it now be a Mini-Cooper filled with DVDs?

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What do you mean a resurgance? My wife's Suburban is really nothing but a
tall station wagon. Well, a tall station wagon, with an extra back seat,
mounted on a truck chassis: but that's beside the point. :-)

<snip>

--
Walter Mallory   walter.mallory@mbda-us.com
Reach, Connect, Celebrate, Grow, Serve

Re: OT:why a group of signals is called a bus?

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<schnip>
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<schnop>

Ever seen a pig on skates? LOL Hilarious picture in my mind.
But you've got to hand it to 'em that you can see 'em fly once
they get the hang of it.... Short sturdy legs. And at that, four
of those. A low center of gravity... Rocksteady...
There's a catch, though... Can you guess what?

Waldemar

P.S. My 12 year old Peugeot 205 Automatic does better than 40
miles to the gallon, and with the present gas prizes I still call that
guzzling... How about yours?



Re: OT:why a group of signals is called a bus?

[...]
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I guess we could update it.

   "Never underestimate the bandwidth of an SUV full of DVDs."

I wonder how long that will last...

Regards,

                               -=Dave
--
Change is inevitable, progress is not.

Re: OT:why a group of signals is called a bus?
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Generally, with proper termination, a bus can be used to transport
DATA in multiple directions from the point of origin.

--
Chuck F ( snipped-for-privacy@yahoo.com) ( snipped-for-privacy@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
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Re: OT:why a group of signals is called a bus?

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Tahoe Area Rapid Transit.

John


Re: OT:why a group of signals is called a bus?
@news.demon.co.uk:

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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

Re: OT:why a group of signals is called a bus?

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Really ?
I thought that you always have a hub between. So only two devices on the
same cable, which is then point to point ...



Re: OT:why a group of signals is called a bus?

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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

Re: OT:why a group of signals is called a bus?
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Think about the bus as an abstract/system concept
rather than the physical/wire.


--
Michael N. Moran           (h) 770 516 7918
5009 Old Field Ct.         (c) 678 521 5460
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Re: OT:why a group of signals is called a bus?

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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!!!
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Re: OT:why a group of signals is called a bus?
@newsreader.visi.com:

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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!"

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True.

--
Walter Mallory   walter.mallory@mbda-us.com
Reach, Connect, Celebrate, Grow, Serve

Re: OT:why a group of signals is called a bus?
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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



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