Datasheet

990
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
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 DDP must be disabled in
order to prevent feeding current to the host. The application should disconnect the transceiver, then remove the pull-up.
40.4.1 I/O Lines
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.
40.4.2 Power Management
The USB device peripheral requires a 48 MHz clock. This clock must be generated by a PLL driven by a clock source
with an accuracy of ± 0.25% (note that the fast RC oscillator cannot be used).
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.
40.4.3 Interrupt
The USB device interface has an interrupt line connected to the Interrupt Controller.
Handling the USB device interrupt requires programming the Interrupt Controller before config-uring the UDP.
Table 40-3. Peripheral IDs
Instance ID
UDP 34