Re: [usb] usb clarifications

[govindsrajan@hotmail.com]

Hi Ravi,

   Here's are the steps to assign an address to a device.

   0. Send USB reset for few bit times.

   1. Setup Stage
          Host sends "setup" token  (addr==0, endp==0) ===> default pipe
          Host sends "data0" token  (wVal contains the address of device)
          Device sends "Ack" if the data was received without any errors 
          like crc error, pid error.

   2. Status Stage
          Host sends "In" token
          Device sends "Data1" pkt with zero data length
          Host sends "Ack" if there was no error in the received data pkt.

    The data stage is not present for "Set_Address" command but may
    be present for other commands.

    Hope this helps.

    Thanks
    Govind


----- Original Message ----- 
From: Ravi Kumar <ravikumar_vlsi@y... > 
To: usb@o...  
Date: Wed, 19 Jun 2002 15:15:38 +0100 (BST) 
Subject: Re: [usb] usb clarifications 

> 
> 
> hi all 
> I have a clarification on usb. 
> Would some tell me 
> 
> 1)what is the packet structure 
> for assigning an address to the device. 
> 
> is the command is 
> set_addres 
> followed by a data phase for  the address to be 
> assigned to device. 
> 
> 
> 2) 
> do we assign a unique address to an endpoint of the 
> device or what ? 
> 
> 
> regards 
> Ravikumar 
> 
> 
>  --- Vikas T Rao  <vikasraot@m... > wrote: > 
> ** Proprietary ** 
> > 
> > hi ravi, 
> > 
> > hub should recognise the device attachment and 
> > detachment. this will be indicated to the host by 
> > the status change endpoint mechanism if it is a hub, 
> > if hub acts as root hub then it will be reported in 
> > the port control and status register. i suggest you 
> > to go through the chapter-->11 refer 11.12 hub 
> > controller. 
> > 
> > ...vikas 
> > 
> > 
> > >>> ravikumar_vlsi@y...  06/17/02 09:45PM 
> >>> 
> > hi all, 
> > I understand that usb host polls devices in frequent 
> > intervals for periodic kind of transfers (namely 
> > Isochronous & Interupt Transfer type) , but with 
> > what 
> > frequency that it polls the Hub's Status endpoint 
> > for 
> > detecting the attachment & Detachement of usb 
> > devices. 
> > 
> > I beleive the frequency that it polls the Hubs 
> > status 
> > Descriptor is relatively higher -- Would u pls 
> > clarify 
> > whether i have understood correctly 
> > 
> > Regards 
> > Ravikumar 
> > 
> > 
> > 
> > 
> > 
> >  --- senthil  nadesan 
> > <senthilnadesan@r... > 
> > wrote: > 
> > > Hello ravi, 
> > >   Gothrough the lines within codes,it is taken 
> > from 
> > > the usb 
> > > specification 1.1 in the page 231. 
> > > 
> > >          "In the downstream direction, hubs 
> > operate 
> > > in a broadcast 
> > > mode. When a hub detects an SOP on its 
> > > upstream port, it establishes connectivity to all 
> > > enabled 
> > > downstream ports. If a port is not enabled, it 
> > does 
> > > not propagate packet signaling downstream." 
> > > 
> > > With regards 
> > > Senthil 
> > > 
> > > 
> > > On Fri, 14 Jun 2002 Ravi Kumar wrote : 
> > > >hi all, 
> > > >In USB . 
> > > >Consider the OUT transaction , 
> > > >will the host controller 
> > > >sends the data to all the devices in broadcast or 
> > > >will it  select particular hub where the devices 
> > is 
> > > >anchored & send the data to that particular hub . 
> > > > 
> > > >Pls reply 
> > > >Regards 
> > > >Ravikumar 
> > > > 
> > > > 
> > > > 
> > > > 
> > > >  --- govindsrajan@h...  wrote: > Hi, 
> > > > > 
> > > > >    During an enumeration process, what should 
> > be 
> > > the 
> > > > > address value in 
> > > > >    the Setup Token. Is it always "zero" or the 
> > > > > address value of the device 
> > > > >    which is being sent in "Set Address" 
> > command 
> > > in 
> > > > > the data phase? 
> > > > > 
> > > > >    SetUp Token (Sync,Pid,Addr,Endp,crc5,Eop) ; 
> > > Addr 
> > > > > = 0 /  [1-128] ? 
> > > > >    Data            (Sync,Pid,Data0,crc16,Eop); 
> > 
> > > // 
> > > > > Data0 has the command 
> > > > > 
> > > > >    If I change the address of a device, what 
> > is 
> > > the 
> > > > > address value in the 
> > > > >    Setup Token. Is it zero or the old value? 
> > > > > 
> > > > >    A quick reply is appreciated. 
> > > > > 
> > > > >    Thanks 
> > > > >    Govind 
> > > > > -- 
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> > > > 
> > > 
> > 
> 
> 
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