at91rm3400 ATMEL Corporation, at91rm3400 Datasheet - Page 397

• Manufacturer Part Number: at91rm3400
• Description: Atmel Advanced At91 Arm Microcontroller
• Manufacturer: ATMEL Corporation

Product Dependencies
I/O Lines
Power
Management
Interrupt
1790A–ATARM–11/03
Note:
The USB physical transceiver is integrated into the product. The bi-directional differential sig-
nals DP and DM are available from the product boundary.
Two I/O lines may be used by the application:
•
•
DP and DM are not controlled by any PIO controllers. The embedded USB physical trans-
ceiver is controlled by the USB device peripheral.
To reserve an I/O line to check VBUS, the programmer must first program the PIO controller to
assign this I/O in input PIO mode.
To reserve an I/O line to control the board pull-up, the programmer must first program the PIO
controller to assign this I/O in output PIO mode.
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 inter-
face with the bus USB signals (recovered 12 MHz domain).
The USB device interface has an interrupt line connected to the Advanced Interrupt Controller
(AIC).
Handling the USB device interrupt requires programming the AIC before configuring the UDP.
One 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 board pull-up on
DP must be disabled in order to prevent feeding current to the host.
One to control the board pull-up on DP. Thus, when the device is ready to communicate
with the host, it activates its DP pull-up through this control line.
For further details on the USB Device hardware implementation, see the specific Product Prop-
erties document.
AT91RM3400
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