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SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

For further details on the USB Device hardware implementation, see the specific Product Properties document.

The USB physical transceiver is integrated into the product. The bidirectional differential signals DDP and DDM are
available from the product boundary.

One I/O line may be used by the application to check that VBUS is still available from the host. Self-powered devices
may use this entry to be notified that the host has been powered off. In this case, the pull-up on DP must be disabled in
order to prevent feeding current to the host. The application should disconnect the transceiver, then remove the pull-up.

The USB pins are shared with PIO lines. By default, the USB function is activated, and pins DDP and DDM are used for
USB. To configure DDP or DDM as PIOs, the user needs to configure the system I/O configuration register
(CCFG_SYSIO) in the MATRIX.

The USB device peripheral requires a 48 MHz clock. This clock must be generated by a PLL with an accuracy of 

±

0.25%.

Thus, the USB device receives two clocks from the Power Management Controller (PMC): the master clock, MCK, used
to drive the peripheral user interface, and the UDPCK, used to interface with the bus USB signals (recovered 12 MHz
domain).

WARNING:  The UDP peripheral clock in the Power Management Controller (PMC) must be enabled before any
read/write operations to the UDP registers including the UDP_TXVC register. 

The USB device interface has an interrupt line connected to the Interrupt Controller. 

Handling the USB device interrupt requires programming the Interrupt Controller before configuring the UDP.

UDP

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