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Question about Slave FIFO

Summary: 4439 Views, 1 Replies, Latest reply by PRJI on 09 Apr 2012 02:12 AM PST

Verified Answers: 0

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Zoidberg posted on 05 Apr 2012 3:32 AM PST

1 Forum Post

Hi, in my design the FIFO is synchronously filled at aobut 6MBs, with streaming data coming from and ADC, with some glue logic in between (it's and SDR application). If I use isochronous endpoint with 1024 size packet and 1 packet per microframe, the bandwidth is roughly 8MBs. Since the USB side is faster than the FIFO side, it means (if I understood correctly, i'm new to USB) that some IN tokens will arrive when no data has been committed yet. What happens in this case? The host will wait or a zero packet length will be sent? 

I could shorten the isochronous packet length to match the bandwidths, 750 size packet gives 6MBs, but my understanding is that it is better to have a faster USB side, in order to avoid full FIFO event and loss of data (there is no other buffer in between). Am I correct?

One last question: when the FIFO goes from full to empty and the flag is de-asserted, is this flag change synchronous with IFCLK or it can happen asynchronously?

Thanks

 

 



 

PRJI posted on 09 Apr 2012 02:12 AM PST
Cypress Employee
473 Forum Posts

  Hi,

       See this http://www.cypress.com/?docID=20041 

       Flag change is synchronous; see timing diagrams in AC Electrical Characteristics section of Datasheet.

Thanks

Prajith



 

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