thanks, some more questions.
(1) SOF and suspend mode
Usually, a USB device will enter suspend mode if it detects there is no activity on the USB bus for more than 3 ms (I assume there is no SOF on the bus as well). But the SOF is sent every 1ms, then at what circumstance, host stops to send SOF.
(2) Can we control Windows to enter suspend mode (stop to send SOF) ?
thanks in advance.