Dear expert,
Customer met a strange problem.
XI is 40MHz. REFCLKSEL1,0 is 11, ULPI_CLK is normal 60MHz.
But USB controller failed to handshake with TUSB1310A. Phenomenon is USB controller send 0x8a 06, ULPI_NXT is HIGH. Then sending 0x8A, 00, ULPI_NXT is always LOW.
But when customer accidently set REFCLKSEL1,0 to 10, XI input is still 40MHz ULPI_CLK become 80MHz.
This is an accident but surprise is handshake become success. Phenomenon is USB controller send 0x8a 06, ULPI_NXT is HIGH. Then sending 0x84, 6d, ULPI_NXT is HIGH. Of course , only handshake succeed. The following USB communication still has error.
The phenomenon are the same for REFCLKSEL1,0 to 00, , XI input is still 40MHz ULPI_CLK become 120MHz. (same as 80MHz case)
Could you guide me how to debug this issue? Why nominal 60MHz ULPI_CLK cannot have handshake success?
Thanks
