AT90USB646 datasheet(270/459 Pages) ATMEL

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270

7593H–AVR–11/08

ATmega32U6/AT90USB64/128

ADDEN is cleared by hardware:

• after a power-up reset,

• when an USB reset is received,

• or when the macro is disabled (USBE cleared)

When this bit is cleared, the default device address 00h is used.

22.8

Suspend, Wake-up and Resume

After a period of 3 ms during which the USB line was inactive, the controller switches to the full-

speed mode and triggers (if enabled) the SUSPI (suspend) interrupt. The firmware may then set

the FRZCLK bit.

The CPU can also, depending on software architecture, enter in the idle mode to lower again the

power consumption.

There are two ways to recover from the “Suspend” mode:

• First one is to clear the FRZCLK bit. This is possible if the CPU is not in the Idle mode.

• Second way, if the CPU is “idle”, is to enable the WAKEUPI interrupt (WAKEUPE set). Then,

as soon as an non-idle signal is seen by the controller, the WAKEUPI interrupt is triggered.

The firmware shall then clear the FRZCLK bit to restart the transfer.

There are no relationship between the SUSPI interrupt and the WAKEUPI interrupt: the WAKE-

UPI interrupt is triggered as soon as there are non-idle patterns on the data lines. Thus, the

WAKEUPI interrupt can occurs even if the controller is not in the “suspend” mode.

When the WAKEUPI interrupt is triggered, if the SUSPI interrupt bit was already set, it is cleared

by hardware.

When the SUSPI interrupt is triggered, if the WAKEUPI interrupt bit was already set, it is cleared

by hardware.

22.9

Detach

The reset value of the DETACH bit is 1.

It is possible to re-enumerate a device, simply by setting and clearing the DETACH bit.

• Setting DETACH will disconnect the pull-up on the D+ or D- pad (depending on full or low

speed mode selected). Then, clearing DETACH will connect the pull-up on the D+ or D- pad.

Figure 22-3. Detach a device in Full-speed:

EN=1

D +

UVREF

D -

Detach, then

Attach

EN=1

D +

UVREF

D -

AT90USB646 Datasheet(PDF) 270 Page - ATMEL Corporation

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