Kinetis MicrocontrollersのトピックUSB ISTAT register

USB ISTAT register

James8 — Wed, 07 Mar 2012 01:49:06 GMT

Hi, I seem to be having a problem clearing the flags in this register... I have read in the datasheet that they are cleared by writing a 1 to the bit, which is counter intuitive but nevermind, but when I do write a 1 (or a 0 for that matter) the register doesn't change, it appears to be read only.

I have tried to use several USB example projects (every one I could find), and none of them work, potentially because of this problem, they all rely on the flags being cleared and thus end up getting stuck in infinite loops etc.

Any ideas?

Re: USB ISTAT register

mjbcswitzerland — Wed, 07 Mar 2012 07:46:14 GMT

Writing 1 to the bit to be cleared is the technique that is used.

Check that the interrupt status register is declared as a byte wide register with volatile attributes.

The USB controller is 99.9% identical to the one in the Coldfire where the same technique is used.

Maybe the USB clock is not configured correctly?

There are USB device examples that can be loaded to KWIKSTIK or Tower board at http://www.utasker.com/SW_Demos.html so that you can check your HW.

Regards

Mark