Hi Ivo,
You could refer to the SOFTHLD description on USB chapter of K60 Reference Manual. According with this part, the value of 74 should be stored on SOFTHLD when the worse case happens (64-byte packets); instead of calculating this value dynamically, as this causes a continuous overwrites to the register, which seems to be causing such behavior.
Hope this will be useful for you.
Best regards!
/Carlos
-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
-----------------------------------------------------------------------------------------------------------------------