AT43USB353M datasheet(82/95 Pages) ATMEL

82 / 95 page

AT43USB353M

3307B–USB–4/04

Global Resume

Global resume is signaled by a J to K state change on Port0. 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.

Remote Wakeup

While the AT43USB353M is in global suspend, resume signaling is also possible through

remote wakeup if the remote wakeup feature is enabled. Remote wakeup is defined as a port

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.

Selective Suspend

and Resume

See section on Hub Port Control Register, HPCON.

Suspend and Resume

Process

Global Suspend

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.

Hardware

Firmware

1.Host stops sending packets

Global suspend signaling detected

Stop downstream signaling

Set GBL SUS bit

→ interrupt

Shut down any peripheral activity

Set Sleep Enable and Sleep Mode bits

of MCUCR

Set GPIO to low power state if required

Set UOVCER bit 2

Execute SLEEP instruction

10. SLEEP bit detected

11. Shut off oscillator

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