Hi all,

in some postings problems are indicated when omitting the 32 KHz clock.

The problems obviously depend on SDK and FX3 silcon revisions.

Can you today recommend to safely omit the 32 Khz clock when there is no need for a watchdog in standby mode?

Regards

Günter

Hi Gunter,

32kHz clock is used by some of the wakeup mechanisms when the device enters low power mode.

So it is recommended to keep if the device needs to support low power modes. You don't have to place it, If low power modes are not needed.

Thanks,

sai krishna.

Hi Sai Krishna,

what about the usb command verifier test necessary for a whql certification. For the verifier I thought you need support of low power mode. Does that mean, that without the 32kHz you can not succeed whql?

thanks,

lumpi

Hi Lumpi,

Yes. USBCV does one suspend resume test on the connected USB device. So, as you said, 32KHz is needed to pass USBCV.

Thanks,

sai krishna.

Hi Sai Krishna,

we tried with older SDK of FX3 and I also tried yet with 1.2.1 if the USB 3.0 CV succeeds. It succeeds and we do not have a 32kHz clock on our hardware. Can you please double check why it should pass the USB 3.0 CV?

thanks,

lumpi

Hi ,

 I am facing some hanging issue (DMA Commit channel buffer failing) when 32KHz Clock is used as Watchdog timer. When it is omitted the issue is not coming. I want to know how to disable the watchdog timer in the firmware.

Thanks,

Kasthuri Rangan V

Hi Sai Krishna,

we tried with older SDK of FX3 and I also tried yet with 1.2.1 if the USB 3.0 CV succeeds. It succeeds and we do not have a 32kHz clock on our hardware. Can you please double check why it should pass the USB 3.0 CV?

Or are the problems while using USB2.0 connection?

thanks,

lumpi

What about 32.768 kHz then?  The docs say +/- 200ppm, so it suggests it won't work.

.

On the other hand, are these really only watchdog timers?

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The reason I ask -- 32.768 kHz is available in a lot more sizes.  32 kHz has pretty limited availability and takes up a fair bit of board space. 

Hi Lumpi, Jake,

I have verified the usefulness of 32KHz crystal with the design and software teams and they confirmed the following:

The wakeup sources that are enabled currently (CY_U3P_SYS_PPORT_WAKEUP_SRC_EN, CY_U3P_SYS_USB_WAKEUP_SRC_EN and
CY_U3P_SYS_UART_WAKEUP_SRC_EN are the various wakeup sources.) don't require this 32kHz crystal to be present. It is required for some reserved wakeup sources which might be enabled in future like OTGID.

So, you can ignore this 32KHz crystal in your present designs.

Thanks,

Sai Krishna.