USB0 FS Host Controller with FRO_HF clock.

johan_carlsson — Fri, 04 Oct 2024 13:16:52 GMT

The documentation is ambiguous in regard to if it's possible to use the FRO_HF clock when using the USB0 Full-speed Host Controller.

UM11126: Table 37.

The currently selected FRO_192 high speed output at 96 MHz. FRO_HF clock is the output of the FRO_192 divided by 2 (96 MHz). Note that this clock can only be used for USB device and is not reliable for USB host timing requirements of the data signaling rate.

AN13449: 4. Hardware design

When using FS USB host, HS USB host/device, external crystal must be connected.

UM11126: 42.5.

Clock: To have the full-speed USB operating, select either the PLL1, or USB PLL, or FRO clock output as the USB0 clock and the clock must be 48 MHz

The text above seems incorrect there is no USB PLL in the full-speed controller, it can also be used with PLL0. It does however state that the FRO clock can be used.

Is it recommended to use the FRO_HF clock with the USB0 Full-Speed Host controller?

Regards, Johan

Re: USB0 FS Host Controller with FRO_HF clock.

Pablo_Ramos — Wed, 09 Oct 2024 19:29:53 GMT

Hi @johan_carlsson,

The FRO_HF is not recommended for USB host because of the +/- 2% accuracy on the FRO (temperature/process/pcb/etc), result may vary. The FRO_HF is recommended in the implementation of a crystal-less FS USB device like in the example of the technical note TN00063.

Since there is no option of crystal-less USB host it is mention on the hardware design that if you want to implement a FS USB host it would be required that the external crystal is connected.

topic Re: USB0 FS Host Controller with FRO_HF clock. in LPC Microcontrollers

USB0 FS Host Controller with FRO_HF clock.

Re: USB0 FS Host Controller with FRO_HF clock.