FLAG Pin State of EZ-USB® FX1™/FX2™/FX2LP™ during a USB Bus Reset – KBA90546

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Question: What is the state of the FLAG pins of EZ-USB® FX1™/FX2™/FX2LP™ during a USB bus reset? What will the state of the FLAG pins be after a USB bus reset?

 

Answer:

During a USB bus reset the endpoint buffers are not affected. The FLAG pins will retain their configured states. If the USB bus reset occurs when there is no firmware on the EZ-USB, then the ports are in the default port I/O and the FLAG pins are not guaranteed to be in any particular state. The above answer holds true for the state of the FLAG pins after USB bus reset as well.

The USB bus reset is handled by ISR_Ures(). This ISR can be modified if any action needs to be performed when a USB bus reset occurs. More details about the FLAG pins and the effect of a USB bus reset on EZ-USB FX1/FX2/FX2LP can be found in the EZ-USB Technical Reference Manual.