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Hi Virendra,

Hi,
The HS transceiver has 45 Ohm Rs (series resistance) and 15KOhm Rpd 
(pull down resistance).
The Rs resistance is connected at the output of the FS/LS driver of the 
HS xcvr. This Rs
resistance is connected both at the downstream and upstream port. So in 
combination they
provide a 90 Ohm impedance match to the USB cable. To signal SE0, a 
strong one, the
downstream port's FS/LS driver drives current through the 45 Ohm Rs.
The Rpd resistances can give only a soft SE0.

For details refer to the Fig 7.1 of USB2.0 specs.

As far as I know the UTMI is only used for the peripheral i.e. on the 
upstream ports. So the
question of driving SE0 doesn't arise. Anyway Linestate[1:0] is an input 
to the SIE and
cannot be driven.

Regards,
Neelabh

Ravi Rajaraman wrote:

> Hi Virendra,
>
> The picture that i see as a USB host is HOST --> PHY ---> USB BUS.
> In this case if the PHY is UTMI, the host has to just keep it in high 
> speed mode with a proper
> combination of xcvr_select and termselect signal. I actually dont 
> remember, but from what i
> remember both should be tied to ground.(just incase check with UTMI 
> spec). When the host
> ties both those signal to ground, the PHY just activates its pulldown 
> resistors( 15k to both D+
> and D-) thereby bringing down the USB bus to SE0 state.
>
> On seeing xcvr select and termselect activating high speed, the 
> default state of the USB bus
> for high speed is SE0, therefore the transceiver reflects this default 
> state in the line state.
>
> I hope this clarifies your query.
>
> Regards,
> Ravi Rajaraman
>
>> From: Virendra <virendradhavale@y...>
>> Reply-To: virendradhavale@y..., "Discussion list about free,open 
>> source USB IP core" <usb@o...>
>> To: usb opencores <usb@o...>
>> Subject: [usb] Driven SE 0
>> Date: Mon, 29 Nov 2004 09:42:37 +0000 (GMT)
>>
>> I would like to know as to how does the USB host drive SE 0 on the 
>> bus. I mean the exact events those happen during driven SE 0. I also 
>> want to know as to how the UTMI responds to generate SE 0 on its 
>> LineState signal.
>>
>> Regards,
>>
>> Virendra.
>>
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>
>
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