Rainbow Electronics AT91CAP9S250A - Manual (Page 872)

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6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
44.4.12.7 Entering Suspend State (Bus Activity)
When a Suspend (no bus activity on the USB bus) is detected, the DET_SUSPD signal in the
UDPHS_STA register is set. This triggers an interrupt if the corresponding bit is set in the
UDPHS_IEN register. This flag is cleared by writing to the UDPHS_CLRINT register. Then the
device enters Suspend Mode.
In this state bus powered devices must drain less than 500 µA from the 5V VBUS. As an exam-
ple, the microcontroller switches to slow clock, disables the PLL and main oscillator, and goes
into Idle Mode. It may also switch off other devices on the board.
The UDPHS device peripheral clocks can be switched off. Resume event is asynchronously
detected.
44.4.12.8 Receiving a Host Resume
In Suspend mode, a resume event on the USB bus line is detected asynchronously, transceiver
and clocks disabled (however the pull-up should not be removed).
Once the resume is detected on the bus, the signal WAKE_UP in the UDPHS_INTSTA is set. It
may generate an interrupt if the corresponding bit in the UDPHS_IEN register is set. This inter-
rupt may be used to wake-up the core, enable PLL and main oscillators and configure clocks.
44.4.12.9 Sending an External Resume
In Suspend State it is possible to wake-up the host by sending an external resume.
The device waits at least 5 ms after being entered in Suspend State before sending an external
resume.
The device must force a K state from 1 to 15 ms to resume the host.