[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [usb] usb clarifications
thanks govind for the reply
Regards
Ravikumar
--- govindsrajan@hotmail.com wrote: >
> Hi Ravi,
>
> If you look at the USB Spec Revision 2.0, (page
> 225) under Control
> Transfer, there is a detailed info. on ocntrol
> transfers. All the Set
> and Get commands fall under this category.
>
> For control Xfer's, there are 2/3 stages, being
> setup stage, data
> stage (may or may not be present) and status
> stage. Each stage
> in turn has 3 token phases, being Setup/Out/In
> token, Data token
> and Handshake token. The sequence is as shown
> below.
>
> 1. Setup Stage
> Host sends setup token indicating to
> device the type of
> transfer is control xfer.
> Host then sends the actual command (Set
> or get command) in
> the Data0 token. This command is 8 bytes
> in length. The actual
> values for the 8 bytes can be found in
> the USB Spec. Each
> command has specific value. If the data
> token goes thru
> succesfully, device will send a ACK.
> 2. Data Stage
> For "Set Address" command there is no
> Data Stage. Other
> commands may have this stage.
> 3. Status Stage
> The direction of Status Stage is always
> opposite to that of the
> previous data phase. For "Set Address"
> command, the previous
> transaction was data token sent by host
> containing the
> command. The host sends an "In" token to
> device.
> The device responds with a zero length
> data pkt if the command
> was ok or sends a STALL or NAK handshake
> depending on data
> pkt error or if the device was busy.
> The host finally sends an "ACK" Handshake
> to complete the
> transaction.
>
> Hope this helps.
>
> Govind
>
>
>
> ----- Original Message -----
> From: Ravi Kumar <ravikumar_vlsi@y... >
> To: usb@o...
> Date: Tue, 25 Jun 2002 15:39:00 +0100 (BST)
> Subject: Re: [usb] usb clarifications
>
> >
> >
> > hi govind thanks fr ur reply
> >
> > pls clarify the folowing
> >
> > 1)
> > where is the set_addrerss command that is
> specified
> > by the host to device , how can the device know
> that
> > am sending a addres to device.
> >
> > 2)
> > u have specified in the previous mail about the
> status
> > stage
> > """"" Device sends "Data1" pkt with zero data
> > length """"""
> >
> > what is the intention of sending this packet
> > pls clarify
> >
> > regards
> > Ravikumar
> >
> > --- govindsrajan@h... wrote: > 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
>
=== message truncated ===
________________________________________________________________________
Want to sell your car? advertise on Yahoo Autos Classifieds. It's Free!!
visit http://in.autos.yahoo.com
--
To unsubscribe from usb mailing list please visit http://www.opencores.org/mailinglists.shtml