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Interesting cycle start behaviour

Harold Okai-Tettey
Prodigy 60 points
Other Parts Discussed in Thread: TSB81BA3E

Hi,

 

Please help me understand a problem. I have 2 devices connected together on a single bus. One of these devices is cycle master and the other transmits isochronous packets. I have noticed that in there a 2 cycles in which isochronous data does not appear on the bus - this happens occasionally. 

On further investigation, I noticed that the a cycle start packet appears on the bus before the cycle start token?? Is this normal? or am I missing something.

 

I'll appreciate any help, Thank you.

 

Please see the attached file image. My devices are using the TSB81BA3E PHY with a custom link layer.

 

Best,

Harold

  • 0
    TI__Guru* 76130 points

    Hello Harold,

    The data captured doesn’t appear abnormal, it is likely that ISOC data is not transmitted every ISOC cycle.  The Firespy snoops the bus, depending on the traffic the cycle start odd/even tokens may not appear in the same location every cycle start.

     

    Is there a specific issue encountered?

    Regards.