USB学习

1. host如何用utmi protocol drive SE0 to reset device

    use OPMODE[1:0] = 2'b10

 

2. host 如何drive chirp K/J to device

     OPMODE[1:0] = 2'b10

      TXVALID = 1

       DATAIN = FF/00 ;

 

3. device如何drive high speed K to host ???

            

4. all signals from OTG controller to PHY are driven at the falling edge of utmi_clk

   all signals from PHY to OTG controller are driven at the rising edge of utmi_clk 

 

5. in OTG protocol, there is avalid (0.8V ~2V), bvalid(0.8V~4V)

    In PHY, there is a session valid compator. The compator threshold select avalid when IDDIG is 0 and select bvalid whe IDDIG is 1. 

    The avalid and  bvalid from PHY are always same and one is the copy of another one.

    So, in OTG controller, we can just use avalid and omit bvalid.  

 

6. The VBUSVALID is always sampled during a session.

    If VBUSVALID change low during a session, the OTG FSM in OTG controller will change to a defined state. (even in suspend mode)