USB_DMAOR
usb_dmac_write(dmac, USB_DMAOR, USB_DMAOR_DME);
dmaor = usb_dmac_read(dmac, USB_DMAOR);
usb_dmac_write(dmac, USB_DMAOR, 0);
usb_dmac_write(dmac, USB_DMAOR, 1);
usb_dmac_write(dmac, USB_DMAOR, 0);