USB spec. says frmaes are transmitted on the bus at 1ms intervals. I
suppose it means they are from the host to the devices. How about the other
way around? Since USB is a half-duplex bus, how will USB maintain those 1ms
intervals?
Thanks
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A frame is just a division in time. Each frame is 1 msec. At the start of
the frame, the host transmits a Start-of-Frame Packet. This notifies
everyone that a new frame is starting and what the frame number is.
After that, with the exception of a bus reset for a device, all successful
communications are a sequence of transmissions in both directions between
the host and device or the device and host. The host always starts each
transaction.
Here are some examples:
Host wants data from a device.
IN host to device: give me my data
Data Device to host: Here
ACK Host to device: Thanks
or
IN Host to device: give me my data
NAK Device to host: I’m not ready yet
Host wants to send data to the device.
OUT Host to device: I’m sending you data
Data Host to device: Here
ACK Device to host: Thanks
You get the general idea. ;=)
Marc Reinig
System Solutions
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Ta H.
Sent: Friday, April 06, 2001 12:08 AM
To: NT Developers Interest List
Subject: [ntdev] half duplex USB
USB spec. says frmaes are transmitted on the bus at 1ms intervals. I
suppose it means they are from the host to the devices. How about the other
way around? Since USB is a half-duplex bus, how will USB maintain those 1ms
intervals?
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So USB frames are not contiguous for either direction right? Is it possible
the frames could be bursty?
From: Marc Reinig
>Reply-To: “NT Developers Interest List”
>To: “NT Developers Interest List”
>Subject: [ntdev] RE: half duplex USB
>Date: Fri, 06 Apr 2001 08:24:33 -0700
>
>A frame is just a division in time. Each frame is 1 msec. At the start of
>the frame, the host transmits a Start-of-Frame Packet. This notifies
>everyone that a new frame is starting and what the frame number is.
>
>After that, with the exception of a bus reset for a device, all successful
>communications are a sequence of transmissions in both directions between
>the host and device or the device and host. The host always starts each
>transaction.
>
>Here are some examples:
>
> Host wants data from a device.
>
> IN host to device: give me my data
> Data Device to host: Here
> ACK Host to device: Thanks
>
> or
>
> IN Host to device: give me my data
> NAK Device to host: I’m not ready yet
>
> Host wants to send data to the device.
>
> OUT Host to device: I’m sending you data
> Data Host to device: Here
> ACK Device to host: Thanks
>
>You get the general idea. ;=)
>
>Marc Reinig
>System Solutions
>
>
>-----Original Message-----
>From: xxxxx@lists.osr.com
>[mailto:xxxxx@lists.osr.com]On Behalf Of Ta H.
>Sent: Friday, April 06, 2001 12:08 AM
>To: NT Developers Interest List
>Subject: [ntdev] half duplex USB
>
>
>USB spec. says frmaes are transmitted on the bus at 1ms intervals. I
>suppose it means they are from the host to the devices. How about the
>other
>way around? Since USB is a half-duplex bus, how will USB maintain those
>1ms
>intervals?
>
>
>
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Frames are just slices in time. They are each 1 msec in length and follow
one after another immediately so that they occur 1,000 times a second.
Each frame can have no data (except SOF) or data going both directions.
Lots of data or little data.
Data generally starts at the start of frame and continues until all
transactions are complete or the frame time is used up.
If there is time left in the frame after all transactions are complete it is
just blank time until the next SOF.
Marc Reinig
System Solutions
-----Original Message-----
From: xxxxx@lists.osr.com
So USB frames are not contiguous for either direction right? Is it possible
the frames could be bursty?
From: Marc Reinig
>A frame is just a division in time. Each frame is 1 msec. At the start of
>the frame, the host transmits a Start-of-Frame Packet. This notifies
>everyone that a new frame is starting and what the frame number is.
>
>After that, with the exception of a bus reset for a device, all successful
>communications are a sequence of transmissions in both directions between
>the host and device or the device and host. The host always starts each
>transaction.
>
>Here are some examples:
>
> Host wants data from a device.
>
> IN host to device: give me my data
> Data Device to host: Here
> ACK Host to device: Thanks
>
> or
>
> IN Host to device: give me my data
> NAK Device to host: I’m not ready yet
>
> Host wants to send data to the device.
>
> OUT Host to device: I’m sending you data
> Data Host to device: Here
> ACK Device to host: Thanks
>
>You get the general idea. ;=)
>
>Marc Reinig
>System Solutions
>
>
>-----Original Message-----
>From: xxxxx@lists.osr.com
>USB spec. says frmaes are transmitted on the bus at 1ms intervals. I
>suppose it means they are from the host to the devices. How about the
>other
>way around? Since USB is a half-duplex bus, how will USB maintain those
>1ms
>intervals?
>
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> Frames are just slices in time. They are each 1 msec in length and follow
one after another immediately so that they occur 1,000 times a second.
Each frame can have no data (except SOF) or data going both directions.
Lots of data or little data.Data generally starts at the start of frame and continues until all
transactions are complete or the frame time is used up.If there is time left in the frame after all transactions are complete it
is
just blank time until the next SOF.
Is it true for isoch traffic only or for things like bulk traffic too?
Max
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This is true for all traffic.
-----Original Message-----
Frames are just slices in time. They are each 1 msec in length and follow
one after another immediately so that they occur 1,000 times a second.Each frame can have no data (except SOF) or data going both directions.
Lots of data or little data.Data generally starts at the start of frame and continues until all
transactions are complete or the frame time is used up.If there is time left in the frame after all transactions are complete it
is
just blank time until the next SOF.
Is it true for isoch traffic only or for things like bulk traffic too?
Max
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So 1ms frames are for bi-directional (host to device and device to host),
right? So if my driver only does READ, the rate I get data from the device
should be longer than 1ms.
From: Marc Reinig
>Reply-To: “NT Developers Interest List”
>To: “NT Developers Interest List”
>Subject: [ntdev] RE: half duplex USB
>Date: Sun, 08 Apr 2001 18:28:05 -0700
>
>Frames are just slices in time. They are each 1 msec in length and follow
>one after another immediately so that they occur 1,000 times a second.
>
>Each frame can have no data (except SOF) or data going both directions.
>Lots of data or little data.
>
>Data generally starts the start of frame and continues until all
>transactions are complete or the frame time is used up.
>
>If there is time left in the frame after all transactions are complete it
>is
>just blank time until the next SOF.
>
>Marc Reinig
>System Solutions
>
>-----Original Message-----
>From: xxxxx@lists.osr.com
>
>So USB frames are not contiguous for either direction right? Is it
>possible
>the frames could be bursty?
>
>
> >From: Marc Reinig
>
> >A frame is just a division in time. Each frame is 1 msec. At the start
>of
> >the frame, the host transmits a Start-of-Frame Packet. This notifies
> >everyone that a new frame is starting and what the frame number is.
> >
> >After that, with the exception of a bus reset for a device, all
>successful
> >communications are a sequence of transmissions in both directions between
> >the host and device or the device and host. The host always starts each
> >transaction.
> >
> >Here are some examples:
> >
> > Host wants data from a device.
> >
> > IN host to device: give me my data
> > Data Device to host: Here
> > ACK Host to device: Thanks
> >
> > or
> >
> > IN Host to device: give me my data
> > NAK Device to host: I’m not ready yet
> >
> > Host wants to send data to the device.
> >
> > OUT Host to device: I’m sending you data
> > Data Host to device: Here
> > ACK Device to host: Thanks
> >
> >You get the general idea. ;=)
> >
> >Marc Reinig
> >System Solutions
> >
> >
> >-----Original Message-----
> >From: xxxxx@lists.osr.com
>
> >USB spec. says frmaes are transmitted on the bus at 1ms intervals. I
> >suppose it means they are from the host to the devices. How about the
> >other
> >way around? Since USB is a half-duplex bus, how will USB maintain those
> >1ms
> >intervals?
> >
>
>
>—
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>To unsubscribe send a blank email to leave-ntdev-$subst(‘Recip.MemberIDChar’)@lists.osr.com
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No.
A frame contains traffic for all devices and any device. INT IN, INT Out,
Bulk IN, Bulk Out, Isoch In, Isoch Out, Control, SOF and anything else I
have missed. They are all lumped together.
There are certain bandwidth restrictions and certain types of transfers have
priority. But, assuming that there is enough bandwidth to handle all
traffic, they will all go in any given frame.
So, if your driver does only READ, it will get a READ every msec, assuming
your device and driver can sustain that rate and the aggregate bandwidth
being used allows it. It has nothing to do with the USB specification or
USB limitations.
Marc Reinig
System Solutions
-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com]On Behalf Of Ta H.
Sent: Monday, April 09, 2001 10:48 AM
To: NT Developers Interest List
Subject: [ntdev] RE: half duplex USB
So 1ms frames are for bi-directional (host to device and device to host),
right? So if my driver only does READ, the rate I get data from the device
should be longer than 1ms.
From: Marc Reinig
>Reply-To: “NT Developers Interest List”
>To: “NT Developers Interest List”
>Subject: [ntdev] RE: half duplex USB
>Date: Sun, 08 Apr 2001 18:28:05 -0700
>
>Frames are just slices in time. They are each 1 msec in length and follow
>one after another immediately so that they occur 1,000 times a second.
>
>Each frame can have no data (except SOF) or data going both directions.
>Lots of data or little data.
>
>Data generally starts the start of frame and continues until all
>transactions are complete or the frame time is used up.
>
>If there is time left in the frame after all transactions are complete it
>is
>just blank time until the next SOF.
>
>Marc Reinig
>System Solutions
>
>-----Original Message-----
>From: xxxxx@lists.osr.com
>
>So USB frames are not contiguous for either direction right? Is it
>possible
>the frames could be bursty?
>
>
> >From: Marc Reinig
>
> >A frame is just a division in time. Each frame is 1 msec. At the start
>of
> >the frame, the host transmits a Start-of-Frame Packet. This notifies
> >everyone that a new frame is starting and what the frame number is.
> >
> >After that, with the exception of a bus reset for a device, all
>successful
> >communications are a sequence of transmissions in both directions between
> >the host and device or the device and host. The host always starts each
> >transaction.
> >
> >Here are some examples:
> >
> > Host wants data from a device.
> >
> > IN host to device: give me my data
> > Data Device to host: Here
> > ACK Host to device: Thanks
> >
> > or
> >
> > IN Host to device: give me my data
> > NAK Device to host: I’m not ready yet
> >
> > Host wants to send data to the device.
> >
> > OUT Host to device: I’m sending you data
> > Data Host to device: Here
> > ACK Device to host: Thanks
> >
> >You get the general idea. ;=)
> >
> >Marc Reinig
> >System Solutions
> >
> >
> >-----Original Message-----
> >From: xxxxx@lists.osr.com
>
> >USB spec. says frmaes are transmitted on the bus at 1ms intervals. I
> >suppose it means they are from the host to the devices. How about the
> >other
> >way around? Since USB is a half-duplex bus, how will USB maintain those
> >1ms
> >intervals?
> >
>
>
>—
>You are currently subscribed to ntdev as: xxxxx@hotmail.com
>To unsubscribe send a blank email to leave-ntdev-$subst(‘Recip.MemberIDChar’)@lists.osr.com
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