at43usb355 ATMEL Corporation, at43usb355 Datasheet - Page 100

• Manufacturer Part Number: at43usb355
• Description: At43usb355 Full-speed Usb Microcontroller With Embedded Hub, Adc And Pwm
• Manufacturer: ATMEL Corporation

Selective Suspend
and Resume
Suspend and Resume
Process
Global Suspend
100
AT43USB355
connect, port disconnect or resume signaling received at a downstream port or, in case of the
embedded function, through an external interrupt.
A remote wakeup initiated at a downstream port is similar in many respects to a global
resume. The USB hardware enables the oscillator/PLL, propagates the RESUME signaling,
and sets the RSM bit of the SPRSR which generates an interrupt. The microcontroller starts
executing where it left off and services the interrupt. As part of the ISR, the firmware clears the
GLB_SUSP bit.
A remote wakeup from the embedded function is initiated through INT0 or the external inter-
rupt, INT1, which enables the oscillator/PLL and the USB hardware. The USB hardware drives
RESUME signaling and sets the FRMWUP and RSM bits of SPRSR which generates an inter-
rupt to the microcontroller. The microcontroller starts executing where it left off and services
the interrupt. As part of the ISR, the firmware clears the GLB SUSP bit.
At completion of RESUME signaling, the USB hardware sets the Port Suspend Status Change
bits of the Hub Port Status Change Registers.
See section on Hub Port Control Register, HPCON.
The Host stops sending packets, the hardware detects this as global suspend signaling and
stops all downstream signaling. Finally, the hardware asserts the GLB_SUSP interrupt.
2. Global suspend signaling detected
3. Stop downstream signaling
4. Set GBL SUS bit → interrupt
10. SLEEP bit detected
11. Shut off oscillator
Hardware
1.Host stops sending packets
5. Shut down any peripheral activity
6. Set Sleep Enable and Sleep Mode bits
7. Set GPIO to low power state if required
8. Set UOVCER bit 2
9. Execute SLEEP instruction
of MCUCR
Firmware
2603G–USB–04/06