Differences in clocking for USB between RM48x and RM46x Hercules MCUs

There is a slight difference in the way the clocks are configured to the USB host/device modules on the RM48 versus RM46 MCUs.



As shown in figures above, on RM48x you need to configure VCLKA3 (same as VCLKA3_S) to be 48MHz for the USB device/host, and then configure the VCLKA3_DIVR to be divide-by-4 to get the 12MHz required by the USB host.

On RM46x, you need to configure VCLKA3_S and VCLKA3_DIVR such that the VCLKA3_DIVR is 48MHz. Then there is a hard-coded divide-by-4 which generates the required 12MHz clock signal for the USB host.

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