AT90USB646 datasheet(447/459 Pages) ATMEL

447 / 459 page

447

7593H–AVR–11/08

ATmega32U6/AT90USB64/128

A so ftware wo rkaround is to wait be foreperforming t he sle ep instru ction: until

TCNT2>OCR2+1.

38. AT90USB647/6 Errata.

• Incorrect interrupt routine exection for VBUSTI, IDTI interrupts flags

• USB Eye Diagram violation in low-speed mode

• Transient perturbation in USB suspend mode generates over consumption

• Spike on TWI pins when TWI is enabled

• High current consumption in sleep mode

• Async timer interrupt wake up from sleep generate multiple interrupts

Incorrect CPU behavior for VBUSTI and IDTI interrupts routines

The CPU core may incorrectly execute the interrupt vector related to the VBUSTI and IDTI

interrupt flags.

Problem fix/workaround

Do not enable these interrupts, firmware must process these USB events by polling VBUSTI

and IDTI flags.

5. USB Eye Diagram violation in low-speed mode

The low to high transition of D- violates the USB eye diagram specification when transmitting

with low-speed signaling.

Problem fix/workaround

None.

4. Transient perturbation in USB suspend mode generates overconsumption

In device mode and when the USB is suspended, transient perturbation received on the

USB lines generates a wake up state. However the idle state following the perturbation does

not set the SUSPI bit anymore. The internal USB engine remains in suspend mode but the

USB differential receiver is still enabled and generates a typical 300µA extra-power con-

sumption. Detection of the suspend state after the transient perturbation should be

performed by software (instead of reading the SUSPI bit).

Problem fix/workaround

USB waiver allows bus powered devices to consume up to 2.5mA in suspend state.

3. Spike on TWI pins when TWI is enabled

100 ns negative spike occurs on SDA and SCL pins when TWI is enabled.

Problem Fix/workaround

No known workaround, enable ATmega32U6/AT90USB64/128 TWI first versus the others

nodes of the TWI network.

2. High current consumption in sleep mode

AT90USB646 Datasheet(PDF) 447 Page - ATMEL Corporation