HX2 FAQS - KBA224052

Version 6

    Author: HirotakaT_91    Version: *C


    Question: Is there a function to disable the USB enumeration by disconnecting the D+ pull-up by CY7C65632 until the configuration is completed?

    Answer: Yes. CY7C65632 complies with the USB specification; therefore, it disconnects the D+ pull-up until the configuration is completed.


    Question: Is VID / PID written in the built-in mask ROM of the HX2VL?

    Answer: Cypress' VID/PID is written in the built-in mask ROM, and cannot be changed.

    If an external EEPROM is used, you can add custom VID/PIDs with the help of the Blaster Utility.


    Question: Do I need to set something when I activate HX2VL with built-in mask ROM setting?

    Answer: No special setting is required.

    HX2VL searches first whether an external EEPROM is connected, and starts up from the built-in mask ROM if EEPROM is not connected.


    Question: How do the current consumption differ in the following two cases?

    Case 1: Only Port 1 and Port 2 are enabled and used. Port 3 and Port 4 are disabled.

    Case 2: All ports (Port 1 to 4) are enabled but only Port 1 and Port 2 are used.

    Answer: The current consumption in these cases differ by a few mA. Current consumption of Case 2 is slightly higher than Case 1. For typical or maximum current consumption, see the “DC Electrical Characteristics” section in the HX2VL datasheet.


    Question: AN72332 recommends using a 100-kΩ pull-up resistor for the power enable (PWR#) pins. Can I use 10-kΩ instead?

    Answer: You can use a 10-kΩ pull-up resistor instead of 100-kΩ. However, note that the leakage current will increase.


    Question: Can D+/D- lines be routed through multiple vias as shown?

    Answer: For USB 2.0, using two vias for routing D+/D- signals is acceptable as shown in this diagram. However, keep in mind that the number of vias affects the impedance and other parameters. Also, keep the vias small (25-mil pad, 10-mil hole), and keep the D+ and D– traces on the same layer, as recommended in AN72332.


    Other Queries

    Question: When does the silicon errata condition for HX2VL (USB device is not recognized properly if a disconnect followed by a connect event happen during hub suspend) occur?

    Answer: As the datasheet mentioned, the condition mentioned in the errata happens after coming out of suspend if the connected downstream (DS) port device is disconnected and connected back to the same DS port during Hub Suspend state.

    The issue is not observed with standard Microsoft driver/class devices such as mouse, keyboard, and mass storage because standard class drivers recover the device using the Port-Reset command when there is a STALL from DS port devices. The condition mentioned in the Errata will occur irrespective of the device speed (Hi-Speed, Full-Speed, or Low-Speed).

    SetPortFeature(PORT_RESET) Hub Class Requests will be issued from a host USB application or driver which binds to the DS port device to recover from a STALL condition. See the datasheet for more information.


    Related Documents



    HX2VL™ Very Low Power USB 2.0 Hub Controller

    Application Notes:


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