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Detecting bus inactivity on the EZUSB | Cypress Semiconductor

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Detecting bus inactivity on the EZUSB

Last Updated: September 22, 2011

If WAKEUP# is tied to ground and suspend mode is inhibited, is there any way to be notified when inactivity is detected on the USB bus? Or is there a register to check to see if the line is inactive?


For the EZUSB, there's no register that flags the user if no bus activity is detected. A suspend interrupt is generated by the core if it detects no bus activity for 3ms (note that if WAKEUP# is tied to ground, you won't get this suspend interrupt).One way you can get around this is to leave WAKEUP# high so that the processor gets a suspend interrupt if it sees no bus activities in 3ms. In the suspend ISR, firmware just doesn't suspend the micro controller(not setting PCON.0).


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