On 9 Aug 2006 05:49:07 -0700, "uzinei" <uzinei@gmail.com> wrote:

>Jura ??:
>
>> "uzinei" <uzinei@gmail.com> wrote in message
>> news:1155109679.664110.75870@m79g2000cwm.googlegroups.com...
>> > I'm designing an audio data transfer circuit using USB 2.0 interface.
>> > I use the Cypress USB tranceiver.
>> > I want to know the worst case transmission speed of USB 2.0.
>> > I already read USB 2.0 Specification, but I cannot found any
>> > information about that.
>> > In USB 2.0 spec., there are only information about Maximum data rate,
>> > 480Mbit per sec.
>> > So, please answer about the worst transmission speed of USB 2.0.
>> > Thanks for any help with this.
>> >
>> > uzinei
>> >
>>
>> 0 Mbit per sec, perhaps ;) ?
>>
>> - Dejan
>
>Thanks for your answer. I think my question is not enough. So, your
>answer is 0 Mbps.
Heh, he is right; definitely the worst possible rate is 0 bits per
second.

>I want to explain my question again. In 1394 interface, there is a
>guaranteed minimum data rate, 100Mbps. 

I have not used 1394, but such a guarantee is impossible. You can
either guarantee to attempt to send at some rate (isochronous or UDP
in ethernet), or guarantee to get data through using retries etc (bulk
or TCP in ethernet). Communication by definition implies failures, so
a medium can either ignore them or retry. Guaranteed success is
impossible.

>Like this, is there a guaranteed
>minimum data rate in USB 2.0 interface?
>I assume that the device is high speed mode and there are only one
>plugged USB 2.0 device in the host PC. In this conditon, is it possible
>that my system have data rate higher than 2Mbit per sec when it is
>received a certain audio data such as speech signal from microphone?

However, assuming things are working properly the maximum rate depends
on both the host and device speed. USB 2.0 is a spec version and has
nothing to do with the actual speed of the interface. A low-speed
mouse could be USB 2.0, so people have confused high speed with USB
2.0.

The USB host dma speed limits the upper end of the high speed. The
spec allows a guaranteed isochronous data rate of 3 1k blocks every
microframe. This works out to about 30 Mbyte/sec for just iso. Bulk
will pack in all available bandwidth so it is quite possible to get on
the order of 40 Mbyte/sec of non-guaranteed speed.

For audio you will probably use isochronous, which means guaranteed
rate, but not perfect delivery. Depending on your device, you should
be able to easily meet the 2 Mbit/sec rate, in fact on a full speed
system you could theoretically hit 8184000 bits per second. That is
using 1023 (yes a funny number) byte packets every ms. So like all
good USB 2.0 devices you should be able to fall back to full speed if
the host cannot handle it and still transfer your 2Mbit/sec data.

Regards, Steve
There is no "x" in my email address.

Jura wrote:
> "uzinei" <uzinei@gmail.com> wrote in message
> news:1155109679.664110.75870@m79g2000cwm.googlegroups.com...
> 
>>I'm designing an audio data transfer circuit using USB 2.0 interface.
>>I use the Cypress USB tranceiver.
>>I want to know the worst case transmission speed of USB 2.0.
>>I already read USB 2.0 Specification, but I cannot found any
>>information about that.
>>In USB 2.0 spec., there are only information about Maximum data rate,
>>480Mbit per sec.
>>So, please answer about the worst transmission speed of USB 2.0.
>>Thanks for any help with this.
>>
>>uzinei
>>
> 
> 
> 0 Mbit per sec, perhaps ;) ?

I suspect it could even be a negative number,
wasting time with the handshaking without ever
transmitting a byte of data (:

Your answer is good for me very much.
Thank you for your help!!

uzinei wrote:
> Jura =EC=9E=91=EC=84=B1:
>
> > "uzinei" <uzinei@gmail.com> wrote in message
> > news:1155109679.664110.75870@m79g2000cwm.googlegroups.com...
> > > I'm designing an audio data transfer circuit using USB 2.0 interface.
> > > I use the Cypress USB tranceiver.
> > > I want to know the worst case transmission speed of USB 2.0.
> > > I already read USB 2.0 Specification, but I cannot found any
> > > information about that.
> > > In USB 2.0 spec., there are only information about Maximum data rate,
> > > 480Mbit per sec.
> > > So, please answer about the worst transmission speed of USB 2.0.
> > > Thanks for any help with this.
> > >
> > > uzinei
> > >
> >
> > 0 Mbit per sec, perhaps ;) ?
> >
> > - Dejan
>
> Thanks for your answer. I think my question is not enough. So, your
> answer is 0 Mbps.
> I want to explain my question again. In 1394 interface, there is a
> guaranteed minimum data rate, 100Mbps. Like this, is there a guaranteed
> minimum data rate in USB 2.0 interface?
> I assume that the device is high speed mode and there are only one
> plugged USB 2.0 device in the host PC. In this conditon, is it possible
> that my system have data rate higher than 2Mbit per sec when it is
> received a certain audio data such as speech signal from microphone?

Actually, the answer of 0 was correct.  USB does not guarentee a
minimum data rate.

During the enumeration process, it is possible for devices to REQUEST a
certain data rate from the host.  The host may accept or deny this
request, and even if it accepts the request it isn't guarenteed that
the requirement will always be met.

Generally speaking, unless the host is extremely encumbered with other
processing or there are a lot of items on the USB port, getting a
sufficient datarate isn't a problem.

Based on the type of information being transfered, you can choose the
type of USB transaction accordingly.  For example, streaming
applications will often times use the isochronous, which I believe
attempts to poll for data at a steady rate, but does not perform error
checking so that data may be lost.  This transaction can obtain very
high data rates.  If the data must be guarenteed, then another
protocol, such as bulk transfer must be used.  If you need data to be
communicated at a steady rate, the interrupt transfer may also apply,
but I believe that interrupt transfers are relatively low in their
bandwidth per packet.

Jura =EC=9E=91=EC=84=B1:

> "uzinei" <uzinei@gmail.com> wrote in message
> news:1155109679.664110.75870@m79g2000cwm.googlegroups.com...
> > I'm designing an audio data transfer circuit using USB 2.0 interface.
> > I use the Cypress USB tranceiver.
> > I want to know the worst case transmission speed of USB 2.0.
> > I already read USB 2.0 Specification, but I cannot found any
> > information about that.
> > In USB 2.0 spec., there are only information about Maximum data rate,
> > 480Mbit per sec.
> > So, please answer about the worst transmission speed of USB 2.0.
> > Thanks for any help with this.
> >
> > uzinei
> >
>
> 0 Mbit per sec, perhaps ;) ?
>
> - Dejan

Thanks for your answer. I think my question is not enough. So, your
answer is 0 Mbps.
I want to explain my question again. In 1394 interface, there is a
guaranteed minimum data rate, 100Mbps. Like this, is there a guaranteed
minimum data rate in USB 2.0 interface?
I assume that the device is high speed mode and there are only one
plugged USB 2.0 device in the host PC. In this conditon, is it possible
that my system have data rate higher than 2Mbit per sec when it is
received a certain audio data such as speech signal from microphone?

"uzinei" <uzinei@gmail.com> wrote in message
news:1155109679.664110.75870@m79g2000cwm.googlegroups.com...
> I'm designing an audio data transfer circuit using USB 2.0 interface.
> I use the Cypress USB tranceiver.
> I want to know the worst case transmission speed of USB 2.0.
> I already read USB 2.0 Specification, but I cannot found any
> information about that.
> In USB 2.0 spec., there are only information about Maximum data rate,
> 480Mbit per sec.
> So, please answer about the worst transmission speed of USB 2.0.
> Thanks for any help with this.
>
> uzinei
>

0 Mbit per sec, perhaps ;) ?

- Dejan