AT32UC3A3256S_1 Datasheet, PDF (648/961 Pages) ATMEL Corporation – AVR32 32-Bit Microcontroller

AT32UC3A3
27.7.3.3
27.7.3.4
27.7.3.5
sumption. The USB pad should be in the Idle state. Once a device is connected, the macro
enters the Ready state, what does not require the USB clock to be activated.
The controller enters the Suspend state when the USB bus is in a “Suspend” state, i.e., when
the host mode does not generate the “Start of Frame (SOF)”. In this state, the USB consumption
is minimal. The host mode exits the Suspend state when starting to generate the SOF over the
USB line.
Device detection
A device is detected by the USBB host mode when D+ or D- is no longer tied low, i.e., when the
device D+ or D- pull-up resistor is connected. To enable this detection, the host controller has to
provide the VBus power supply to the device by setting the VBUSRQ bit (by writing a one to the
VBUSRQS bit).
The device disconnection is detected by the host controller when both D+ and D- are pulled
down.
USB reset
The USBB sends a USB bus reset when the user write a one to the Send USB Reset bit in the
Host General Control register (UHCON.RESET). The USB Reset Sent Interrupt bit in the Host
Global Interrupt register (UHINT.RSTI) is set when the USB reset has been sent. In this case, all
the pipes are disabled and de-allocated.
If the bus was previously in a “Suspend” state (the Start of Frame Generation Enable (SOFE) bit
in UHCON is zero), the USBB automatically switches it to the “Resume” state, the Host Wake-
Up Interrupt (HWUPI) bit in UHINT is set and the SOFE bit is set in order to generate SOFs or
micro SOFs immediately after the USB reset.
At the end of the reset, the user should check the USBSTA.SPEED field to know the speed run-
ning according to the peripheral capability (LS.FS/HS)
Pipe reset
A pipe can be reset at any time by writing a one to the Pipe n Reset (PRSTn) bit in the UPRST
register. This is recommended before using a pipe upon hardware reset or when a USB bus
reset has been sent. This resets:
• The internal state machine of this pipe
• The receive and transmit bank FIFO counters
• All the registers of this pipe (UPCFGn, UPSTAn, UPCONn), except its configuration (ALLOC,
PBK, PSIZE, PTOKEN, PTYPE, PEPNUM, INTFRQ in UPCFGn) and its Data Toggle
Sequence field in the Pipe n Status register (UPSTAn.DTSEQ).
The pipe configuration remains active and the pipe is still enabled.
The pipe reset may be associated with a clear of the data toggle sequence. This can be
achieved by setting the Reset Data Toggle bit in the Pipe n Control register (UPCONn.RSTDT)
(by writing a one to the Reset Data Toggle Set bit in the Pipe n Control Set register
(UPCONnSET.RSTDTS)).
In the end, the user has to write a zero to the PRSTn bit to complete the reset operation and to
start using the FIFO.
32072A–AVR32–03/09
648