Clock for both USB and ENET ?

[Glogov_Kolac]

Is there a possibility to run USB (48MHz) and Ethernet (require 50 or 25 MHz) with system clock of 100 MHz . I am afraid that USB and Ethernet can't work simultaneosly due to the diferent clock requirements ? !

[Glogov_Kolac]

I am just consider TWRk60N512 demo which use both USB and Ethernet at the same time. It seems that in this project a external clock (50MHz) is used to clock ENET directly and that clock is used for 96 System clock which suplies USB. Am i right ?

[mjbcswitzerland]

Hi

I don't know which demo you are referring to but that does make sense.

It is necessary to use 50MHz from the PHY when working with 100MHz Ethernet (due to clock synchronisation) and so the tower kit has jumpers to allow the PHY's 50MHz clock to drive the Kinetis K60 clock input - see also http://www.utasker.com/docs/KINETIS/uTaskerV1.4_Kinetis_demo.pdf (chapter 7) for details and jumper settings.

Regards

Mark

[Mohsin455]

Hi All,

           I am using a 25 MHz clock source (instead of 50MHz present on TWRk60N512 ). I want ot generate 96MHz system clock so that I can also use the USB.

Can we generate a system clock on 96MHz using 25 MHz clock source ? Please advise.

Regards,

Mohsin

[mjbcswitzerland]

Hi

When Ethernet and USB are required together the 50MHz (or 25MHz) clock source can be used to generate 96MHz system clock. This is then suitable for the USB clock (by dividing it down to 48MHz).

100MHz can not be used as system clock, but the difference is fairly small.

To run at 100MHz system clock, an external 48MHz clock can be applied to the USB_CLKIN input when the chip used supportes this.

Regards

Mark