NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
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Revision V1.30
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5.22.3 Block Diagram
USB 2.0
Protocol
controller
4K Buffer
USB
transceiver
UTMI
interface
12-EPs
DMA
registers
Control-
EP
Registers
USB Device Controller
USB_DP
USB_DM
AHB Bus
Figure 5.22-1 USB Device Controller Block Diagram
5.22.4 Basic Configuration
USB device clock source is derived from PLL and USB PHY. User has to set the PLL related
configurations before USB device enabled. Set the USBD (CLK_HCLKEN[19]) bit to enable USB
device clock.
In addition, USB device needs a clock from USB PHY for USB 2.0 high speed operation. User has to
set PHYEN (USBD_PHYCTL[9]) high to enable USB PHY.
5.22.5 Functional Description
Operation of different In-transfer modes
5.22.5.1
The data for any in-transfer is written into the internal buffer when in turn is sent to the host on receipt
of an in-token. There are three different modes by which the data sent to the host is validated by CPU.
Auto-Validation Mode
Manual-Validation Mode
Fly Mode
Auto-Validation Mode
5.22.5.2
If an endpoint is selected to be operating in auto-validation mode, the endpoint responds only with
data payload to be equal to EPMPS register. The endpoint controller wait until the amount of data is
equal to EPMPS value and then validates the data. If CPU needs to send a short-packet at the end of
a transfer, the SHORTTXEN bit of USBD_EPxRSPCTL[6] should be set. When this bit set, any
remaining data in the buffer is validated and is sent to the host, for the forthcoming in-token.
This mode requires least intervention of CPU, as most of the work is done by the USB device