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Message
From: Marc Reinig<mreinig@p...>
Date: Mon Apr 12 17:48:30 CEST 2004
Subject: [usb] 2.0 Hub
Read chapters 8 and 11 of the spec about split transactions and the hub
state machine. Basically, it is broadcast to all high speed devices,
identifying packets headed for a full/low speed device. It is interpreted
by any high speed hub which has a high speed link to the host. The hub then
converts it to full/low speed packets and broadcasts that to any full/low
speed devices attached, including full speed hubs, and on down the line,
going to all attached full/low speed devices, until the packet eventually
finds the full/low speed device with that address. All other full/low speed
devices ignore the packet.
Marc Reinig
System Solutions
-----Original Message-----
From: usb-bounces@o... [mailto:usb-bounces@o...]On
Behalf Of M. AbuKhater
Sent: Monday, April 12, 2004 7:15 AM
To: Discussion list about free, open source USB IP core
Subject: RE: [usb] 2.0 Hub
hi
"A high speed hub makes the speed conversion from high to full/low speed
for the full/low speed device. "
Well, since the hub broadcasts, I don't think it can do speed conversion
for all packets (USB2.0 is 40 times faster than 1.1), so how does it know
that a certain packet is directed to this Full-speed device?
Does the hub keeps the address and speed of each device connected to it as
a database inside it? if so why does it broadcast ?
Abukhater
Marc Reinig <mreinig@p...> wrote:
Actually I dashed that off too quick.
High speed traffic is broadcast to all downstream high speed devices.
If there is a low or full speed device down stream of a high speed hub, it
will be attached as a low or full speed device either directly to a high
speed port, or through a full speed hub, which will be connected as a full
speed device. A high speed hub makes the speed conversion from high to
full/low speed for the full/low speed device. It effectively acts like a
host controller in this case. See 11.14 in the USB spec.
Marc Reinig
System Solutions
-----Original Message-----
From: usb-bounces@o... [mailto:usb-bounces@o...]On
Behalf Of Marc Reinig
Sent: Sunday, April 11, 2004 7:46 PM
To: Discussion list about free,open source USB IP core
Subject: RE: [usb] 2.0 Hub
-----Original Message-----
From: usb-bounces@o... [mailto:usb-bounces@o...]On
Behalf Of M. AbuKhater
Sent: Sunday, April 11, 2004 2:09 PM
To: usb@o...
Subject: [usb] 2.0 Hub
happy easter all;
lets say a USB2.0 hub is connected to a host , with many high-,
full- and low-speed devices connected to it.
> as indicated in the USB system architecture , a full speed packet
> is heared only by full speed devices , same for low- high-speed
devices.
> does this mean that the host sends low and full speed frames to
high speed hub?
No, a high speed host communicates with a high speed device at high
speed. The hub is a high speed device.
> if not how does the hub knows which packet is should go to which
device?
Uh. The device address?
Marc Reinig
System Solutions
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