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AR# 47538

Zynq-7000 AP SoC, USB - Device mode does not generate a port change interrupt when session is no longer valid

Description

The USB controller in device mode and acting as a self-powered device does not generate a port change interrupt when the session is no longer valid (VBUS not present).

To work around this, software can enable the B session end interrupt to detect when the VBUS voltage level drops.

Solution

Impact:

Minor. Refer to the work-around.

Work-around:

The two-step work-around is described in the Work-around Details.

Configurations Affected:

Systems that use the USB controller in Device mode.

Device Revision(s) Affected: All. No plan to fix. Refer to (Xilinx Answer 47916) - Zynq-7000 AP SoC Silicon Revision Differences.


Work-around Details

The following software steps can be followed to detect a disconnect from the host:

  • Enable the B Session End Interrupt. Set usb.OTGSC[BSEIE] = 1.
  • Monitor for an interrupt status using usb.OTGSC [BSEIS].

Note: The VBUS comparator interrupts are de-bounced for 1ms, so it will take 1ms to 2ms for the interrupt to be asserted from the time the disconnect has occurred.

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
47916 Zynq-7000 AP SoC Devices - Silicon Revision Differences N/A N/A
AR# 47538
Date Created 05/23/2012
Last Updated 04/15/2013
Status Active
Type Design Advisory
Devices
  • Zynq-7000
  • XA Zynq-7000
  • Zynq-7000Q