Re: [usb] Regarding Frames and Microframes

["Veeresh" <veeresh@umsl-india.com>]

Title: Message

Hi Thierry,

 

Thanks for your clarification and I expect same kind of help in future.

 

Thanking you once again.

 

Rgds,

Veeresh     

 

----- Original Message -----

From: Thierry LEROUX

To: 'usb@opencores.org'

Sent: Tuesday, February 26, 2002 3:27 PM

Subject: RE: [usb] Regarding Frames and Microframes

Hi,

These frames are "token only" transactions. They do not need any ACK or NAK to be handled.

There is a 8 bits PID + 11 bits of frame # + 5 bits CRC (= 3 Bytes).

The Frame # is a 11 bits system wide time frame. Use of it is function dependent. You can imagine to use it to maintain a common system wide time frame (For example to synchronise audio equipments ...).

The "tick" time is 1 ms.

In addition, there is µ-frame ticks (125 µs) if the function is 2.0 compatible. In that case you need some local computation to create a 15 bits counter.

We found this SOF very useful for synchronization over the whole bus and between connected devices.

 

I hope this help.

 

Thierry

-----Original Message-----
From: Veeresh [mailto:veeresh@umsl-india.com]
Sent: lundi 25 février 2002 19:57
To: usb@opencores.org
Subject: [usb] Regarding Frames and Microframes

Hi all,

 

     I am Veeresh newly joined this mailing list. While going through the USB Spec. 2.0, I got some doubts in Start Of Frame (SOF). As these frames are token only transactions, what is the significance of these frames? What the 11-bit frame indicates?

 

Thanks and regards,
Veeresh